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diff --git a/etc/etc.i386/INSTALL.ata b/etc/etc.i386/INSTALL.ata new file mode 100644 index 00000000000..d9e249b4585 --- /dev/null +++ b/etc/etc.i386/INSTALL.ata @@ -0,0 +1,921 @@ + ATA/ATA-1/ATA-2/IDE/EIDE/etc FAQ + + Part 1 of ? -- The Basics + + Version 0b -- 7 Feb 95 + + by Hale Landis -- landis@sugs.tware.com + +Note: Major changes from the previous version are marked by a + "!" at the left margin on the first line of the changed + paragraph. + +First the "legal" stuff... + + 1) This FAQ is not intended to replace any other FAQ on this + subject but is an attempt to provide historical and technical + information about the ATA interface. + + 2) This FAQ is not an endorsement of any vendor's product(s). + + 3) This FAQ is not a recommendation to purchase any vendor's + product(s). + + 4) Every effort is made to insure that all of the information + presented here is not copyrighted, not proprietary and + unrestricted. + + 4) When opinions are stated they are clearly identified, + including the person's name and email address. Such opinions + are offered as long as they contribute to the understanding of + the subject being discussed. No "flames" allowed. + +This is the first version of this FAQ. It will take some time to +get all the significant information into it so it will be rapidly +growing and changing during the next several weeks or months. I +don't even know how many parts there will be yet! Versions will +be numbered with simple integer numbers (no 1.1, 1.2, etc) +starting at 0. + +If you have a question that is not answered here or if you have +unrestricted material that you would like to contribute, please +email it to landis@sugs.tware.com. DO NOT send material that is +copyrighted, proprietary or otherwise restricted in any way -- I +can't use such material in this document. + +I don't have FTP access to anything at this time so I leave it to +others to put this at the appropriate FAQ FTP sites. + +About myself: Until recently I worked for Seagate where I was +one of several people that attended the ATA, ATA-2, PCMCIA and +SFF meetings for Seagate. I was also the manager of a software +development group that created much of the engineering test +software for ATA hard disk drives. I am now a consultant and I +still attend the ATA-2 meetings. + +Table of Contents +----------------- + +Part 1 - The Basics + + Glossary + Basic Questions + +Part 2 - BIOS and Drivers + + TBD + + +Glossary +-------- + +Read and understand these terms. You will be lost and confused +if you don't! Many of these are describe in much greater detail +in other parts of this FAQ. + +ATA or AT Attachment + + ATA is the proper and correct name for what most people call + IDE. In this document, ATA refers to all forms of ATA (ATA-1, + ATA-2, etc, IDE, EIDE, etc). The ATA interface uses a single + 40-conductor cable in most desktop systems. + +ATA-1 + + ATA-1 is the common name of the original ATA (IDE) + specification. ATA-1 is not an official standard yet. Final + approval is pending. + +ATA-2 or ATA Extensions + + ATA-2 is the common name of the new ATA specification. ATA-2 + is still in early draft form and has not been submitted for + approval as an official standard. + +ATA-3 + +! ATA-3 is the common name of a future version of the ATA + specification. The ATA-3 working group has held several + meeting but the only things adopted so far are a DMA + version of the Identify command, a description of + "device 1 only configurations" and a set of "security" + commands. + +! There is much discussion going on concerning merging ATA-3 + with ATAPI. This will require some kind of "command overlap" + capability. The details of this are consumming much of the + meeting time. + +ATAPI or ATA Packet Interface + + ATAPI is a proposed new interface specification. Initially it + will probably be used for CD-ROM and tape devices. It uses + the ATA hardware interface at the physical level but uses a + subset of the SCSI command set at the logical level. The + ATAPI specification work is currently being done in the SFF + committee. + +! The ATAPI folks have delayed forwarding their CD-ROM + specification from SFF to X3T10 so the X3T10 ATAPI working + group has nothing to work on yet and have held no meetings. + +! Block Mode + +! Block mode is the name given to the use of the ATA Read + Multiple and Write Multiple commands. These commands generate + a single interrupt to the host system for each block of + sectors transfered. The traditional Read Sectors and Write + Sectors commands generate an interrupt to the host for each + sector transfered. + +CAM (Common Access Method) Committee + + The Common Access Method committee, now disbanded, worked on + two specifications: the CAM SCSI and CAM ATA specifications. + Both specifications were forwarded to the X3T9 committee for + further work years ago. + +CHS or Cylinder/Head/Sector + + CHS is the old and traditional way to address data sectors on + a hard disk. This style of addressing relates a sector's + address to the position of the read/write heads. In today's + ATA devices, all sector addresses used by the host are logical + and have nothing to do with the actual physical position of + the sector on the media or the actual position of the + read/write heads. + +Command Block +Control Block + + These are names given to the I/O register interface used by + ATA devices. It refers to a set of I/O registers, or I/O + ports and I/O port addresses used to program the device. + These names replace the older term Task File. + +DMA or Direct Memory Access + + DMA is a method of data transfer between two devices that does + not use the system's main processor as part of the data path. + DMA requires lots of hardware: a DMA arbitration unit, a DMA + data transfer unit and host bus signals that enable the DMA + controller to assume control of the host system's bus. When + the DMA controller has control of the host system's bus, it + moves data between the two devices by generating the + appropriate bus read/write cycles. For the ATA READ DMA + command this means generating an I/O read cycle and then a + memory write cycle for each 16-bit word being transferred. + For the ATA WRITE DMA command, a memory read cycle is followed + by an I/O write cycle for each 16-bit word transferred. + +EIDE or Enhanced IDE + + EIDE is a marketing program started by Western Digital to + promote certain ATA-2 features including ATAPI. WD has + encouraged other product vendors to mark their products as + "EIDE compatible" or "EIDE capable". + +ESDI + + See MFM. + +Fast ATA + + Fast ATA is a Seagate marketing program used to promote + certain ATA-2 features in newer ATA devices. Seagate has + encouraged other product vendors to mark their products as + "Fast ATA compatible" or "Fast ATA capable". + +Host or Host System + + The computer system that the ATA device is attached to. + +HBA or Host Bus Adapter or Host Adapter + + The hardware that converts host bus signals to/from ATA + interface signals. An ATA-1 host adapter is generally a very + simple piece of hardware. An ATA-2 host adapter can be simple + or complex. + +IDE + + IDE can mean any number of things: Imbedded Device (or Drive) + Electronics (yes, you can spell embedded with an "i"), + Intelligent Device (or Drive) Electronics, etc. The term IDE + is the trademark of someone (Western Digital does not claim + IDE as theirs but they do claim EIDE). Many hard disk vendors + do not use IDE to describe their products to avoid any + trademark conflicts. + +LBA or Logical Block Addressing + + LBA is a newer (for ATA it is newer) way to address data + sectors on a hard disc. This style of addressing uses a + 28-bit binary number to address a sector. LBA numbers start + at zero. In today's ATA devices, all sector addresses used by + the host are logical and have nothing to do with the actual + physical location of the sector on the media. + +Local Bus + + Usually this refers to the processor's local bus in a high + performance computer system. Usually the processor, the + external processor instruction/data cache, the main memory + controller and the bridge controller for the next low speed + system bus, for example, a PCI bus, are located on the local + bus. Lower speed local buses may have connectors that allow + the attachment of other devices. For example, the VL-Bus is a + local bus that can allow attachment of video, SCSI or ATA + controllers. It is very difficult to attach other devices to + high speed (say faster than 100MHz) local buses due to + electrical restrictions that come into play at those higher + speeds. + +Master + + ATA device 0. Device 0, the master, is the "master" of + nothing. See Slave. + +Megabyte or MB + + Megabyte or MB is 1,000,000 bytes or 10^6 bytes. IT IS NOT + 1,048,576 bytes or 2^20 bytes, repeat NOT! + +MFM + + In this document MFM refers to any of the older hard disk + controller interfaces, MFM, RLL and ESDI. It is used to + describe any hard disk controller that uses the Task File + interface on the host side and the ST506/ST412 interface + on the drive side. + +OS + + Operating System. + +PC Card ATA +PCMCIA + + We can thank the Personal Computer Memory Card International + Association for the PC Card specification. The PCMCIA is a + nonprofit industry association. The PC Card ATA + specification is another form of the ATA interface used by + PCMCIA compatible ATA devices. This interface uses the PCMCIA + 68-pin connector. Most 68-pin ATA devices are dual mode -- + they can operate as either a PCMCIA PC Card ATA device or as a + 68-pin ATA device. + +PCI + + We can thank Intel and the other members of the PCI committee + for the PCI bus specification. PCI is intended to be the next + high performance computer bus. PCI is not generally described + as a processor local bus. + +PIO or Programmed Input/Output + + PIO is a method of data transfer between two devices that uses + the system's main processor as part of the data path. On + x86 systems, the REP INS and REP OUT instructions + implement this data transfer method. INS reads and I/O port + and writes the data into memory. OUTS reads data from memory + and writes the data to an I/O port. Each time an INS or OUTS + instruction is executed, the memory address is updated. The + REP prefix causes the instructions to be repeated until a + counter reaches zero. + +RLL + + See MFM. + +Slave + + ATA device 1. Device 1, the slave, is a "slave" to nothing. + See Master. + +Task File + + This is the name given to the I/O register interface used by + MFM controllers. It refers to a set of I/O registers, or I/O + ports and I/O port addresses used to program the controller. + In ATA, this name has been replaced by the terms Command Block + and Control Block. + +SCSI + + See the SCSI FAQ. + +SFF or Small Form Factor + + The SFF committee is an ad hoc committee formed by most of the + major storage device and system vendors to set standards for + the physical layout of hard disk and other devices. SFF has + published many specifications that describe the physical + mounting and connector specifications for hard disk devices, + including ATA devices. During a brief period of time when the + X3T9 committee was not doing much work on the ATA-1 interface, + the SFF committee published several specifications that were + not really part of the original SFF charter. Most, if not + all, of these nonphysical specifications have now been + incorporated into the latest X3T9 or X3T10 ATA specifications. + ATAPI is currently an SFF specification. + +ST506 and ST412 + + This is the common name for the hard disk controller to hard + disk drive interface used by MFM, RLL and ESDI controllers and + disk drives. ST stands for Seagate Technology. The ST506 and + ST412 were the Seagate products that set the de facto + standards for this interface many years ago. This interface + is composed of two cables: a 34-conductor and a 20-conductor + cable. + +VESA and VL-Bus + + We can thank the Video Electronics Standards Association for + the VESA Local Bus or VL-Bus specification. The VL-Bus is one + example of a local bus. VESA is a nonprofit industry + association like the PCMCIA. + +WG or Working Group + + The actual work on various specifications and standards + documents within the X3T9, X3T10 and SFF committees happens in + working group meetings. Most WG meetings are held monthly. + +X3T9 and X3T10 + + These are the names of the official standards committees that + have worked on the ATA-1 and ATA-2 specifications. X3T9 was + responsible for the SCSI and ATA-1 specifications and + standards. X3T10 has replaced X3T9 and is now responsible for + the current SCSI and ATA specifications and standards work. + +528MB + + This term is used in this document to describe the capacity + boundary that exists in most x86 system software. This + boundary limits the size of an ATA disk drive to 528MB. For + cylinder/head/sector style addressing of disk data sectors, + this number is computed as follows: + + a) the number of cylinders are limited to 1024, numbered + 0-1023. + + b) the number of heads (per cylinder) are limited to 16, + numbered 0-15, + + c) the number of sectors (per track) are limited to 63, + numbered 1-63. + + d) a sector is 512 bytes, + + e) 528MB means the following values: + + ( 1024 * 16 * 63 ) or 1,032,192 data sectors + + or + + ( 1024 * 16 * 63 * 512 ) or 528,482,304 bytes. + +68-pin ATA + + This refers to a variation of the ATA interface that uses the + PCMCIA 68-pin physical interface but does not use the PCMCIA + electrical or logical interface. Most 68-pin ATA devices are + dual mode -- they can operate as either a PCMCIA PC Card ATA + device or as a 68-pin ATA device. This interface was + developed within the SFF committee and is now included in + ATA-2. + +Basic Questions +--------------- + +### Where did ATA come from? + + What we now call the ATA-1 interface was developed for Compaq + many years ago by Imprimus (then part of CDC, now part of + Seagate) and Western Digital. The first ATA-1 hard disk + drives were made by Imprimus but it was Conner that made the + interface so popular. + +### How is ATA different from MFM? + + From the host software standpoint, ATA is very much like the + Task File interface used by MFM controllers. A properly + written host software driver should not notice any difference + between the MFM Task File interface and the ATA Command Block + interface while doing basic commands such as Read/Write + Sectors. + + At the hardware level, ATA uses a single cable between a host + bus adapter and the ATA device, where the MFM controller + interface uses two cables between the controller and the + drive. + + In the MFM environment, the controller is one piece of + hardware and the drive another piece of hardware. Most likely + these two pieces of hardware are from different vendors. The + MFM controller is dependent on the design of both the host bus + and on the drive. + + In the ATA environment, the host adapter is the one piece of + hardware that is dependent on the host system bus design. The + ATA interface is (mostly) system independent. All of the + hard disk controller and drive logic is contained in the ATA + device hardware. This gives the hard disk designer complete + control over both the controller and drive functions. + +### Why is ATA so popular? + + Two basic things make ATA so popular today: cost and hard + disk drive technology. An ATA-1 host adapter is cheap, + usually much less than $25US and it uses only one cable. On + the technology side, current hard disk features, such as, + defect handling, error recovery, zone recording, cache + management and power management require that the controller be + fully integrated with the read/write channel, the servo system + and spindle hardware of the disk drive. + +### What are the basics of the ATA interface? + + The ATA interface is a very simple interface based on an ISA + bus I/O device architecture. The interface consists of two + sets of I/O registers, mostly 8-bit, for passing command and + status information. The registers are like a set of mail + boxes with a door on front and back connected such that both + doors can not be open at the same time. The front door is + open when the Busy bit in the Status register is zero and the + host can read and write the registers. The back door is open + when the Busy bit in the Status register is one and the ATA + device can read or write the registers. + + The physical interface contains just enough signals for a 16 + bit data bus, five register address bits, and a few control + signals like read register, write register and reset. + + ATA devices look like traditional hard disk + drives even though some are not really a hard disc with + rotating platters. User data is recorded in 512 byte sectors. + Each sector has a sector address. There are two ways to + express sector addresses: by cylinder/head/sector (CHS) or by + logical block address (LBA). CHS is standard, LBA is optional. + +### What is EIDE or Fast ATA? + + Both are marketing programs used to promote various ATA-2 + features, mostly the faster data transfer rates defined by + ATA-2. + + --- + + WD defines EIDE as: + + * Support for drives larger than 528MB. + + * Support for two connectors to allow up to four drives. + + * Support for CD-ROM and tape peripherals. + + * Support for 11.1/16.6 Mbytes/second, I/O Channel Ready PIO + data transfers. + + * Support for 13.3/16.6 Mbytes/second, DMA data transfers. + + --- + +???Seagate defines Fast ATA as: + + * Support for PIO mode 3 (11.1 MB/sec) and DMA mode 1(13.3 + MB/sec). + + * Support for Multi-sector [Read/Write Multiple] transfers. + + * Support for >528 MB. + + * Support for Identify Drive Extensions & Set Transfer Mode + Extensions. + + * Backward compatibility with ATA-1. + + --- + + What does all of this mean to us? + + Support for the ATA-2 high speed PIO and DMA data transfer + modes is both a hardware and software issue. + + Support for more than one hard disc controller (or ATA host + adapter) requires the BIOS and/or the operating system to + support more than one Task File or Command/Control Block + register set on the host bus. + + The 528MB problem is due to the original design of the x86 + BIOS which limits cylinders to 1024 and sectors to 63. The + ATA interface allows up to 65,535 cylinders, 16 heads and 255 + sectors -- that's about 136GB (137GB if is LBA is used). + Support for devices over 528MB requires the BIOS and/or + operating system to support some form of CHS translation. + Note that LBA alone does not solve this problem (in fact, + LBA may make things more complex). + + Support for CD-ROM and tape will probably be done via the + ATAPI interface which uses a different command structure than + ATA. That makes ATAPI another host software issue. + +### What does an ATA-1 host adapter do? + + An ATA-1 host adapter is a simple piece of logic whose main + purpose is to reduce the system bus address lines from 12 (or + more) down to 5. It may also buffer some signals giving some + degree of electrical isolation between the host bus (usually + an ISA or EISA bus) and the ATA bus. In ATA-1, the ATA + interface is controlled directly by the host bus so that all + timings are controlled by the host bus timing. + +### What does an ATA-2 host adapter do? + + This answer is complex because it depends on how smart your + ATA-2 host adapter is. First, an ATA-2 host adapter supports + the ATA-2 higher speed data transfer rates. That requires + that the host adapter is attached to something other than an + ISA or EISA bus. Second, an ATA-2 host adapter may perform + 32-bit wide transfers on the host bus. This requires FIFO + logic and data buffers in the host adapter. Third, an ATA-2 + host adapter may use a different data transfer protocol on the + host side than is used on the ATA device side. + +! ### Can I put an ATA-2 device on an ATA-1 host adapter? +! ### Can I put an ATA-1 device on an ATA-2 host adapter? + + The answer to both questions is yes, as long as the electrical + timing specifications of the device are not violated. In + general it is impossible for an ATA-1 host adapter to violate + the specifications of an ATA-2 device. It is possible for an + ATA-2 host adapter to violate the timing specifications of an + ATA-1 device but this is not common. Hoever, host adapter + hardware design errors or software driver bugs can cause such + a problem. The result will be corrupted data read or written + to the ATA-1 device. + +! ### I have an ATA-2 host adapter with an ATA-2 device. I want to +! ### add an ATA-1 device to this host adapter. Can I run the ATA-2 +! ### device in its ATA-2 data transfer modes? + + Sorry, *NO* you can *NOT* run the new drive in its faster data + transfer modes. Be very careful, most of the ATA-2 host + adapter vendors don't have anything in their setup + documentation or software to prevent this sort of thing. + + When you run the new drive at a data transfer speed that is + faster than the older drive can support, you are violating the + electrical interface setup and hold times on the older drive. + There is no telling what the older drive will do about this, + but you are asking for data corruption and other nasty + problems on your older drive. + +### How many disk controllers and/or ATA host adapters and/or +### SCSI host adapters can I put in my system? + + From a hardware standpoint -- as many as you want as long as + there are no I/O port address, memory address or interrupt + request signal conflicts. From a software standpoint it is a + whole different story. + + First the simple x86 system hard disk controller + configurations... + + a) 1 ATA with 1 or 2 drives at I/O port addresses + 1Fxh/3Fxh using interrupt request 14 (IRQ14). + + b) 1 ATA with 1 drive at I/O port addresses 1Fxh/3Fxh + using interrupt request 14 (IRQ14) plus a SCSI with 1 drive. + + c) 1 SCSI with 1 or 2 drives. + + Other configurations are possible but are most likely not + supported in the system or SCSI host adapter BIOS. And if its + not supported at the BIOS level, it is unlikely to be + supported by an operating system, especially DOS. The primary + reason the above configurations are so restrictive is that the + original IBM x86 BIOS supported only one MFM controller with a + maximum of 2 drives. This restriction was then coded into + much x86 software including many early version of DOS. The + configurations above work because they don't break this old + rule. + + Just remember this -- most systems will always boot from + the first drive on the first controller. In a) that is + ATA drive 0, in b) that is ATA drive 0, in c) that is + SCSI drive 0. + + And now the more complex configurations... + + Once you go beyond the three configurations above all bets are + off. Most likely you will need operating system device + drivers in order to access any drives beyond the first two. + And now your real problems start especially if you like to run + more than one operating system! + + If you do run more than one OS, then you need equivalent + drivers for each system if you would like to access all the + drives. Plus it would be nice if all the drivers configured + the drives in the same manner and supported all the possible + partitioning schemes and partition sizes. It would be + especially nice if a driver would not destroy the data in a + partition just because it did not understand the file system + format in that partition. + + One of the things EIDE promotes is BIOS support for up to four + ATA devices -- 2 ATA host adapters each with 1 or 2 drives. + The first would be at I/O port addresses 1Fxh/3Fxh using + interrupt request 14 (IRQ14) and the second at I/O port + addresses 17xh/37xh using interrupt request 15 (IRQ15). + Acceptance of this configuration has not been spreading like + wild fire through the BIOS world. + + Lets look at a two complex configurations... + + a) 1 ATA with 2 drives and 1 SCSI with 1 or more drives. + + Nice configuration. The ATA drives would be supported by the + system BIOS and the SCSI drives may be, could be, should be, + supported by the SCSI host adapter BIOS but probably not. So + in order to use the 2 SCSI drives you probably have to disable + the BIOS on the SCSI card and then load a device driver in + CONFIG.SYS. And because the SCSI BIOS is disabled, you then + need a SCSI driver for that other OS you run. + + b) 2 ATA with 1 or 2 drives on each. + + Also a nice configuration. But because the system BIOS + probably only supports the first controller address, you'll + need a DOS device driver loaded in CONFIG.SYS in order to + access the drives on the second controller. You'll need that + driver even if there is only one drive on the first + controller. You also need a similar driver to support the + second controller in your other OS. + + Note: I understand that OS/2 does support both MFM/ATA + controller addresses and does allow up to four drives -- I + have not confirmed this for myself. + +! ### Are disk drives the only ATA devices? + + No. Over the years there have been ATA tape drives, ATA + CD-ROMS and other strange devices. Most of these are expected + to be added to an existing ATA host adapter as the second + device (device 1) with an existing ATA disk drive (device 0). + In general these require software drivers to operate with your + OS. + + Now, we have ATAPI CD-ROM and tape devices that can be placed + on an ATA host adapter. And soon we should see system + motherboard BIOS support for booting from an ATAPI CD-ROM + device. The general idea is that an ATAPI device can coexist + with an ATA device on the same cable. + +! ### What can be done to improve ATA device performance? + + A difficult question. But the first step is usually to reduce + the number of interrupts that the host sees during a read or + write command. ATA disk drives have three types of read/write + commands: + + * Read Sectors / Write Sectors -- These commands are the old + traditional data transfer commands. These commands generate + one interrupt to the host for each sector transfered. These + are PIO data in and PIO data out commands which use the host + processor to transfer the data. + + * Read Multiple / Write Multiple -- These commands where + defined in ATA-1 but were not used very much until recently. + These commands generate one interrupt to the host for each + block of sectors transfered. The number of sector per block + is generally 4, 8 or 16. However, when 1 sector per block is + used, these commands are the same as the Read/Write Sectors + commands. These are PIO data in and PIO data out commands + which use the host processor to transfer the data. + + * Read DMA / Write DMA -- These commands where defined in + ATA-1 but were not used very much until recently. The main + reason for not using them was that x86 system DMA transfer + rates are much slower than PIO. However, these command do + generate a single interrupt at the completion of the command. + + Now see the next question... + +! ### What else can be done to improve ATA device performance? +! ### -or- +! ### What is PIO mode "x" ? + + An even more difficult question. The second step is usually + to increase the rate at which the host transfers data. + + (Ahh... I can see the funny look on your face from here. You + are saying to yourself: "the rate at which the host transfers + data? doesn't this guy have things backwards?" Read on...) + + The rate at which data is transferred to or from an ATA device + is determined by only one thing: the PIO or DMA cycle time + the host uses. No, the drive does not have much to do with + this! The only requirement is that the host not exceed the + minimum PIO or DMA cycle times that the device supports. For + example, during a PIO read command when the device signals an + interrupt to the host this means that the device is waiting + for the host to read the next sector or block of sectors from + the drive. The host must execute a REP INSW instruction to do + transfer the data. The rate at which the host executes this + instruction determines the PIO cycle time. Technically, for a + read command, the cycle time is the time from the host + assertion of the I/O Read signal to the next time the host + asserts the I/O Read signal. + + Be careful when looking at the table below -- the data rate is + the data transfer rate achieved while transfering the sector + or block or sectors. It is an "instantanous" data rate. The + overall data transfer rate for a command includes many time + consuming events such as the amount of time the host requires + to process an interrupt. Note that on many fast ATA drives + today, the time it takes the host to process an interrupt is + frequently greater than the time required to transfer the + sector of block of sectors for that interrupt! It is not + uncommon for the host overhead to reduce the data rate to 1/2 + or 1/3 of the instantanous rate shown here. + + The ATA PIO modes are defined as follows: + + PIO min cycle data comment + mode time rate + + 0 ???ns ?MB the rate at which a system + running at 4.77MHZ could + execute the REP INSW. + + 1 ???ns ?MB the rate at which a system + running at 6MHz could + execute the REP INSW. + + 2 240ns 8MB the rate at which a system + running at 8MHz could + execute the REP INSW. + + 3 180ns 13MB requires an ATA-2 + host adapter. + + 4 120ns 16MB requires an ATA-2 + host adapter. + + The complete description of the PIO (and DMA modes is much + more complex and will be cover in more detail later in this + FAQ. + +### Do I need BIOS or OS drivers to support more than 528MB? + + Warning: Read the previous question before reading this one. + + Maybe, probably, yes. The answer to this *very* complex and + will be discussed in detail in Part 2. Here is the brief + answer... + + A traditional x86 system BIOS supports only CHS mode + addressing with cylinders limited to 1024, heads limited to 16 + and sectors limited to 63. This allows addressing of drives + up to 528MB. These limitations come from the INT 13 + read/write calls that combine a 10-bit cylinder number with a + 6-bit sector number into a 16-bit register. + + Note that this is entirely a software problem: the ATA + interface supports up to 65,535 cylinders, 16 heads and 255 + sectors. + + While the head number usually requires only 4-bits, up to 6 or + 8 bits are available in the INT 13 interface. This fact has + allowed the SCSI folks to support big drives by increasing the + number of heads above 16. The SCSI host adapter BIOS converts + this "fake" CHS address to a different CHS or an LBA when it + issues a read/write command to the drive. The following table + shows some approximate drives sizes and the "fake" CHS + parameters that you may see from a SCSI BIOS: + + cyl head sector size + + 1024 16 63 512MB + 1024 32 63 1GB + 512 64 63 1GB + 1024 64 63 2GB + 1024 256 63 8GB + + The last entry represents the largest possible drive that + a traditional INT 13 BIOS can support. + + The system BIOS folks *must* start supporting drives over + 528MB in their BIOS by implementing some type of CHS + translation. To date, few systems have such BIOS. And here + is the bad part: Microsoft says that the BIOS *must* + support it in order to use it in their OS. The algorithm is + simple (but warning: this is not the complete algorithm!): + + INT 13 input action ATA interface + + cyl number "multiply" by n modified cyl number + head number "divide" by n modified head number + sector number nothing sector number + + The value of n must be selected such that the modified head + number is less than 16. + + LBA addressing at the hard disk drive level or at the BIOS or + driver level is another solution. This solution will probably + not be popular for several more years. It requires that the + BIOS people implement a new INT 13 interface, called the + Microsoft/IBM Extensions and that the OS people start using + this new BIOS interface. Few system BIOS support this + alternative interface today. Without this new interface, LBA + support at the hard disk drive level is not required. + + So most of us have older systems without much possibility of + getting a BIOS upgrade, so what do we do? Well we must obtain + one of the many driver products that are on the market that + live in one of the disk boot sectors and "take over" the + system BIOS INT 13 with an INT 13 that supports the + translation. The biggest problem with this is that the + replacement INT 13 BIOS must live someplace in memory. For + DOS based systems, it can usually live at the top of the 640K + of memory and DOS is made to think that that part of memory, + usually around 8K bytes, does not exist. But the protected + mode OS's don't like this and usually wipe out the driver when + they load their kernel. So if you plan to run multiple OS's + on your system, buyer beware! + + Then there is the Windows problem: the standard FastDisk + driver in Windows does *not* support such translation schemes + and can not be enabled. So make sure the driver you + purchase also comes with a Windows FastDisk replacement. + + Buyer beware! + +### Do I need BIOS or OS drivers to support the ATA-2 data +### transfer rates? + + Warning: Read the previous two questions before reading this + one. + + Maybe, probably, yes. The answer to this *very* complex and + will be discussed in detail in Part 2. Here is the brief + answer... + + If you have a new ATA drive that supports the advanced PIO or + DMA data transfer rates (ATA-2 PIO Mode 3 or 4, or, ATA-2 DMA + Mode 1 or 2) then you also must have a new ATA host adapter + that attaches to the VL-Bus or PCI bus or some other high + speed bus (probably a 32-bit bus) in your system. That host + adapter has I/O registers of its own that are used to control + its advanced features. Controlling those advanced features + requires software -- either in the system INT 13 BIOS or in a + INT 13 BIOS on the host adapter card or in a driver loaded + via the boot record or later by your OS. + + Depending on how that host adapter works you may also + need a Windows FastDisk replacement in order to use the high + speed data transfer modes in Windows. + + Buyer beware! + +### I just purchased a new high speed host adapter for my VL-Bus +### (or PCI bus) system and a new 540MB hard disk. How do I get +### full use out of all this new hardware? + + Did you read the previous three questions? + + You need BIOS or driver software and a Windows FastDisk + replacement. These *must* support both CHS translation + (because your drive is over 528MB) and the host adapter + hardware (to use the high speed data transfer rates). + + Some drivers on the market today use LBA addressing on the + ATA interface to get over 528MB. This may make your disk + partition(s) unreadable by another OS. + + Check the hardware and software specifications of the product + before you buy it! Ask lots of questions -- you probably get + lots of incorrect or misleading answers -- be prepared for + that! If you plan to run something other than DOS and + Windows, especially if you plan a "dual boot" or "boot + manager" environment, be real careful. + + Buyer beware! + + OPINION: I know of only one product that supports all of this + new hardware, supports over 528MB *and* supports most of the + current OS's that are shipping including several in shipping + in beta form. The product is from a small two person company + that is trying to sell the product on an OEM basis and not in + the retail market. - Hale Landis <landis@sugs.tware.com> + +/end part 1/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// diff --git a/etc/etc.i386/INSTALL.chs b/etc/etc.i386/INSTALL.chs new file mode 100644 index 00000000000..e93a748c1a0 --- /dev/null +++ b/etc/etc.i386/INSTALL.chs @@ -0,0 +1,890 @@ + How It Works -- CHS Translation + + Plus BIOS Types, LBA and Other Good Stuff + + Version 4a + + by Hale Landis (landis@sugs.tware.com) + +THE "HOW IT WORKS" SERIES + +This is one of several How It Works documents. The series +currently includes the following: + +* How It Works -- CHS Translation +* How It Works -- Master Boot Record +* How It Works -- DOS Floppy Boot Sector +* How It Works -- OS2 Boot Sector +* How It Works -- Partition Tables + + +Introduction (READ THIS!) +------------------------- + +This is very technical. Please read carefully. There is lots of +information here that can sound confusing the first time you read +it. + +Why is an understanding of how a BIOS works so important? The +basic reason is that the information returned by INT 13H AH=08H +is used by FDISK, it is used in the partition table entries +within a partition record (like the Master Boot Record) that are +created by FDISK, and it is used by the small boot program that +FDISK places into the Master Boot Record. The information +returned by INT 13H AH=08H is in cylinder/head/sector (CHS) +format -- it is not in LBA format. The boot processing done by +your computer's BIOS (INT 19H and INT 13H) is all CHS based. + +Read this so that you are not confused by all the false +information going around that says "LBA solves the >528MB +problem". + +Read this so that you understand the possible data integrity +problem that a WD EIDE type BIOS creates. Any BIOS that has a +"LBA mode" in the BIOS setup could be a WD EIDE BIOS. Be very +careful and NEVER chage the "LBA mode" setting after you have +partitioned and installed your software. + +History +------- + +Changes between this version and the preceeding version are +marked by "!" at left margin of the first line of a changed +or new paragraph. + +Version 4 -- BIOS Types 8 and 10 updated. + +Version 3 -- New BIOS types found and added to this list. More + detailed information is listed for each BIOS type. A section + describing CHS translation was added. + +Version 2 -- A rewrite of version 1 adding BIOS types not + included in version 1. + +Version 1 -- First attempt to classify the BIOS types and + describe what each does or does not do. + +Definitions +----------- + +* 528MB - The maximun drive capacity that is supported by 1024 + cylinders, 16 heads and 63 sectors (1024x16x63x512). This + is the limit for CHS addressing in the original IBM PC/XT + and IBM PC/AT INT 13H BIOS. + +* 8GB - The maximum drive capacity that can be supported by 1024 + cylinders, 256 heads and 63 sectors (1024x256x63x512). This + is the limit for the BIOS INT 13H AH=0xH calls. + +* ATA - AT Attachment -- The real name of what is widely known + as IDE. + +* CE Cylinder - Customer Engineering cylinder. This is the + last cylinder in P-CHS mode. IBM has always reserved this + cylinder for use of disk diagnostic programs. Many BIOS do + not account for it correctly. It is of questionable value + these days and probably should be considered obsolete. + However, since there is no industry wide agreement, beware. + There is no CE Cylinder reserved in the L-CHS address. Also + beware of diagnostic programs that don't realize they are + operating in L-CHS mode and think that the last L-CHS cylinder + is the CE Cylinder. + +* CHS - Cylinder/Head/Sector. This is the traditional way to + address sectors on a disk. There are at least two types + of CHS addressing: the CHS that is used at the INT 13H + interface and the CHS that is used at the ATA device + interface. In the MFM/RLL/ESDI and early ATA days the CHS + used at the INT 13H interface was the same as the CHS used at + the device interface. + + Today we have CHS translating BIOS types that can use one CHS + at the INT 13H interface and a different CHS at the device + interface. These two types of CHS will be called the logical + CHS or L-CHS and the physical CHS or P-CHS in this document. + L-CHS is the CHS used at the INT 13H interface and P-CHS is + the CHS used at the device interface. + + The L-CHS used at the INT 13 interface allows up to 256 heads, + up to 1024 cylinders and up to 63 sectors. This allows + support of up to 8GB drives. This scheme started with either + ESDI or SCSI adapters many years ago. + + The P-CHS used at the device interface allows up to 16 heads + up to 65535 cylinders, and up to 63 sectors. This allows + access to 2^28 sectors (136GB) on an ATA device. When a P-CHS + is used at the INT 13H interface it is limited to 1024 + cylinders, 16 heads and 63 sectors. This is where the old + 528MB limit originated. + + ATA devices may also support LBA at the device interface. LBA + allows access to approximately 2^28 sectors (137GB) on an ATA + device. + + A SCSI host adapter can convert a L-CHS directly to an LBA + used in the SCSI read/write commands. On a PC today, SCSI is + also limited to 8GB when CHS addressing is used at the INT 13H + interface. + +* EDPT - Enhanced fixed Disk Parameter Table -- This table + returns additional information for BIOS drive numbers 80H and + 81H. The EDPT for BIOS drive 80H is pointed to by INT 41H. + The EDPT for BIOS drive 81H is pointed to by INT 46H. The + EDPT is a fixed disk parameter table with an AxH signature + byte. This table format returns two sets of CHS information. + One set is the L-CHS and is probably the same as returned by + INT 13H AH=08H. The other set is the P-CHS used at the drive + interface. This type of table allows drives with >1024 + cylinders or drives >528MB to be supported. The translated + CHS will have <=1024 cylinders and (probably) >16 heads. The + CHS used at the drive interface will have >1024 cylinders and + <=16 heads. It is unclear how the IBM defined CE cylinder is + accounted for in such a table. Compaq probably gets the + credit for the original definition of this type of table. + +* FDPT - Fixed Disk Parameter Table - This table returns + additional information for BIOS drive numbers 80H and 81H. + The FDPT for BIOS drive 80H is pointed to by INT 41H. The + FDPT for BIOS drive 81H is pointed to by INT 46H. A FDPT does + not have a AxH signature byte. This table format returns a + single set of CHS information. The L-CHS information returned + by this table is probably the same as the P-CHS and is also + probably the same as the L-CHS returned by INT 13H AH=08H. + However, not all BIOS properly account for the IBM defined CE + cylinder and this can cause a one or two cylinder difference + between the number of cylinders returned in the AH=08H data + and the FDPT data. IBM gets the credit for the original + definition of this type of table. + +* LBA - Logical Block Address. Another way of addressing + sectors that uses a simple numbering scheme starting with zero + as the address of the first sector on a device. The ATA + standard requires that cylinder 0, head 0, sector 1 address + the same sector as addressed by LBA 0. LBA addressing can be + used at the ATA interface if the ATA device supports it. LBA + addressing is also used at the INT 13H interface by the AH=4xH + read/write calls. + +* L-CHS -- Logical CHS. The CHS used at the INT 13H interface by + the AH=0xH calls. See CHS above. + +* MBR - Master Boot Record (also known as a partition table) - + The sector located at cylinder 0 head 0 sector 1 (or LBA 0). + This sector is created by an "FDISK" utility program. The MBR + may be the only partition table sector or the MBR can be the + first of multiple partition table sectors that form a linked + list. A partition table entry can describe the starting and + ending sector addresses of a partition (also known as a + logical volume or a logical drive) in both L-CHS and LBA form. + Partition table entries use the L-CHS returned by INT 13H + AH=08H. Older FDISK programs may not compute valid LBA + values. + +* OS - Operating System. + +* P-CHS -- Physical CHS. The CHS used at the ATA device + interface. This CHS is also used at the INT 13H interface by + older BIOS's that do not support >1024 cylinders or >528MB. + See CHS above. + +Background and Assumptions +-------------------------- + +First, please note that this is written with the OS implementor +in mind and that I am talking about the possible BIOS types as +seen by an OS during its hardware configuration search. + +It is very important that you not be confused by all the +misinformation going around these days. All OS's that want to be +co-resident with another OS (and that is all of the PC based OS's +that I know of) MUST use INT 13H to determine the capacity of a +hard disk. And that capacity information MUST be determined in +L-CHS mode. Why is this? Because: 1) FDISK and the partition +tables are really L-CHS based, and 2) MS/PC DOS uses INT 13H +AH=02H and AH=03H to read and write the disk and these BIOS calls +are L-CHS based. The boot processing done by the BIOS is all +L-CHS based. During the boot processing, all of the disk read +accesses are done in L-CHS mode via INT 13H and this includes +loading the first of the OS's kernel code or boot manager's code. + +Second, because there can be multiple BIOS types in any one +system, each drive may be under the control of a different type +of BIOS. For example, drive 80H (the first hard drive) could be +controlled by the original system BIOS, drive 81H (the second +drive) could be controlled by a option ROM BIOS and drive 82H +(the third drive) could be controlled by a software driver. +Also, be aware that each drive could be a different type, for +example, drive 80H could be an MFM drive, drive 81H could be an +ATA drive, drive 82H could be a SCSI drive. + +Third, not all OS's understand or use BIOS drive numbers greater +than 81H. Even if there is INT 13H support for drives 82H or +greater, the OS may not use that support. + +Fourth, the BIOS INT 13H configuration calls are: + +* AH=08H, Get Drive Parameters -- This call is restricted to + drives up to 528MB without CHS translation and to drives up to + 8GB with CHS translation. For older BIOS with no support for + >1024 cylinders or >528MB, this call returns the same CHS as + is used at the ATA interface (the P-CHS). For newer BIOS's + that do support >1024 cylinders or >528MB, this call returns a + translated CHS (the L-CHS). The CHS returned by this call is + used by FDISK to build partition records. + +* AH=41H, Get BIOS Extensions Support -- This call is used to + determine if the IBM/Microsoft Extensions or if the Phoenix + Enhanced INT 13H calls are supported for the BIOS drive + number. + +* AH=48H, Extended Get Drive Parameters -- This call is used to + determine the CHS geometries, LBA information and other data + about the BIOS drive number. + +* the FDPT or EDPT -- While not actually a call, but instead a + data area, the FDPT or EDPT can return additional information + about a drive. + +* other tables -- The IBM/Microsoft extensions provide a pointer + to a drive parameter table via INT 13H AH=48H. The Phoenix + enhancement provides a pointer to a drive parameter table + extension via INT 13H AH=48H. These tables are NOT the same + as the FDPT or EDPT. + +Note: The INT 13H AH=4xH calls duplicate the older AH=0xH calls +but use a different parameter passing structure. This new +structure allows support of drives with up to 2^64 sectors +(really BIG drives). While at the INT 13H interface the AH=4xH +calls are LBA based, these calls do NOT require that the drive +support LBA addressing. + +CHS Translation Algorithms +-------------------------- + +NOTE: Before you send me email about this, read this entire + section. Thanks! + +As you read this, don't forget that all of the boot processing +done by the system BIOS via INT 19H and INT 13H use only the INT +13H AH=0xH calls and that all of this processing is done in CHS +mode. + +First, lets review all the different ways a BIOS can be called +to perform read/write operations and the conversions that a BIOS +must support. + +! * An old BIOS (like BIOS type 1 below) does no CHS translation + and does not use LBA. It only supports the AH=0xH calls: + + INT 13H (L-CHS == P-CHS) ATA + AH=0xH --------------------------------> device + (L-CHS) (P-CHS) + +* A newer BIOS may support CHS translation and it may support + LBA at the ATA interface: + + INT 13H L-CHS ATA + AH=0xH --+--> to --+----------------> device + (L-CHS) | P-CHS | (P-CHS) + | | + | | P-CHS + | +--> to --+ + | LBA | + | | + | L-CHS | ATA + +--> to -----------------+---> device + LBA (LBA) + +* A really new BIOS may also support the AH=4xH in addtion to + the older AH\0xH calls. This BIOS must support all possible + combinations of CHS and LBA at both the INT 13H and ATA + interfaces: + + INT 13H ATA + AH=4xH --+-----------------------------> device + (LBA) | (LBA) + | + | LBA + +--> to ---------------+ + P-CHS | + | + INT 13H L-CHS | ATA + AH=0xH --+--> to --+------------+---> device + (L-CHS) | P-CHS | (P-CHS) + | | + | | P-CHS + | +--> to --+ + | LBA | + | | + | L-CHS | ATA + +--> to -----------------+---> device + LBA (LBA) + +You would think there is only one L-CHS to P-CHS translation +algorithm, only one L-CHS to LBA translation algorithm and only +one P-CHS to LBA translation algorithm. But this is not so. +Why? Because there is no document that standardizes such an +algorithm. You can not rely on all BIOS's and OS's to do these +translations the same way. + +The following explains what is widely accepted as the +"correct" algorithms. + +An ATA disk must implement both CHS and LBA addressing and +must at any given time support only one P-CHS at the device +interface. And, the drive must maintain a strick relationship +between the sector addressing in CHS mode and LBA mode. Quoting +the ATA-2 document: + + LBA = ( (cylinder * heads_per_cylinder + heads ) + * sectors_per_track ) + sector - 1 + + where heads_per_cylinder and sectors_per_track are the current + translation mode values. + +This algorithm can also be used by a BIOS or an OS to convert +a L-CHS to an LBA as we'll see below. + +This algorithm can be reversed such that an LBA can be +converted to a CHS: + + cylinder = LBA / (heads_per_cylinder * sectors_per_track) + temp = LBA % (heads_per_cylinder * sectors_per_track) + head = temp / sectors_per_track + sector = temp % sectors_per_track + 1 + +While most OS's compute disk addresses in an LBA scheme, an OS +like DOS must convert that LBA to a CHS in order to call INT 13H. + +Technically an INT 13H should follow this process when +converting an L-CHS to a P-CHS: + + 1) convert the L-CHS to an LBA, + 2) convert the LBA to a P-CHS, + +If an LBA is required at the ATA interface, then this third +step is needed: + + 3) convert the P-CHS to an LBA. + +All of these conversions are done by normal arithmetic. + +However, while this is the technically correct way to do +things, certain short cuts can be taken. It is possible to +convert an L-CHS directly to a P-CHS using bit a bit shifting +algorithm. This combines steps 1 and 2. And, if the ATA device +being used supports LBA, steps 2 and 3 are not needed. The LBA +value produced in step 1 is the same as the LBA value produced in +step 3. + +AN EXAMPLE + +Lets look at an example. Lets say that the L-CHS is 1000 +cylinders 10 heads and 50 sectors, the P-CHS is 2000 cylinders, 5 +heads and 50 sectors. Lets say we want to access the sector at +L-CHS 2,4,3. + +* step 1 converts the L-CHS to an LBA, + + lba = 1202 = ( ( 2 * 10 + 4 ) * 50 ) + 3 - 1 + +* step 2 converts the LBA to the P-CHS, + + cylinder = 4 = ( 1202 / ( 5 * 50 ) + temp = 202 = ( 1202 % ( 5 * 50 ) ) + head = 4 = ( 202 / 50 ) + sector = 3 = ( 202 % 50 ) + 1 + +* step 3 converts the P-CHS to an LBA, + + lba = 1202 = ( ( 4 * 5 + 4 ) * 50 ) + 3 - 1 + +Most BIOS (or OS) software is not going to do all of this to +convert an address. Most will use some other algorithm. There +are many such algorithms. + +BIT SHIFTING INSTEAD + +If the L-CHS is produced from the P-CHS by 1) dividing the +P-CHS cylinders by N, and 2) multiplying the P-CHS heads by N, +where N is 2, 4, 8, ..., then this bit shifting algorithm can be +used and N becomes a bit shift value. This is the most common +way to make the P-CHS geometry of a >528MB drive fit the INT 13H +L-CHS rules. Plus this algorithm maintains the same sector +ordering as the more complex algorithm above. Note the +following: + + Lcylinder = L-CHS cylinder being accessed + Lhead = L-CHS head being accessed + Lsector = L-CHS sector being accessed + + Pcylinder = the P-CHS cylinder being accessed + Phead = the P-CHS head being accessed + Psector = P-CHS sector being accessed + + NPH = is the number of heads in the P-CHS + N = 2, 4, 8, ..., the bit shift value + +The algorithm, which can be implemented using bit shifting +instead of multiply and divide operations is: + + Pcylinder = ( Lcylinder * N ) + ( Lhead / NPH ); + Phead = ( Lhead % NPH ); + Psector = Lsector; + +A BIT SHIFTING EXAMPLE + +Lets apply this to our example above (L-CHS = 1000,10,50 and +P-CHS = 2000, 5, 50) and access the same sector at at L-CHS +2,4,3. + + Pcylinder = 4 = ( 2 * 2 ) + ( 4 / 5 ) + Phead = 4 = ( 4 % 5 ) + Psector = 3 = 3 + +As you can see, this produces the same P-CHS as the more +complex method above. + +SO WHAT IS THE PROBLEM? + +The basic problem is that there is no requirement that a CHS +translating BIOS followed these rules. There are many other +algorithms that can be implemented to perform a similar function. +Today, there are at least two popular implementions: the Phoenix +implementation (described above) and the non-Phoenix +implementations. + +SO WHY IS THIS A PROBLEM IF IT IS HIDDEN INSIDE THE BIOS? + +Because a protected mode OS that does not want to use INT 13H +must implement the same CHS translation algorithm. If it +doesn't, your data gets scrambled. + +WHY USE CHS AT ALL? + +In the perfect world of tomorrow, maybe only LBA will be used. +But today we are faced with the following problems: + +* Some drives >528MB don't implement LBA. + +* Some drives are optimized for CHS and may have lower + performance when given commands in LBA mode. Don't forget + that LBA is something new for the ATA disk designers who have + worked very hard for many years to optimize CHS address + handling. And not all drive designs require the use of LBA + internally. + +* The L-CHS to LBA conversion is more complex and slower than + the bit shifting L-CHS to P-CHS conversion. + +* DOS, FDISK and the MBR are still CHS based -- they use the + CHS returned by INT 13H AH=08H. Any OS that can be installed + on the same disk with DOS must understand CHS addressing. + +* The BIOS boot processing and loading of the first OS kernel + code is done in CHS mode -- the CHS returned by INT 13H AH=08H + is used. + +* Microsoft has said that their OS's will not use any disk + capacity that can not also be accessed by INT 13H AH=0xH. + +These are difficult problems to overcome in today's industry +environment. The result: chaos. + +DANGER TO YOUR DATA! + +See the description of BIOS Type 7 below to understand why a +WD EIDE BIOS is so dangerous to your data. + + +The BIOS Types +-------------- + +I assume the following: + +a) All BIOS INT 13H support has been installed by the time the OS + starts its boot processing. I'm don't plan to cover what + could happen to INT 13H once the OS starts loading its own + device drivers. + +b) Drives supported by INT 13H are numbered sequentially starting + with drive number 80H (80H-FFH are hard drives, 00-7FH are + floppy drives). + +And remember, any time a P-CHS exists it may or may not account + for the CE Cylinder properly. + +I have identified the following types of BIOS INT 13H support as +seen by an OS during its boot time hardware configuration +determination: + +BIOS Type 1 + + Origin: Original IBM PC/XT. + + BIOS call support: INT 13H AH=0xH and FDPT for BIOS drives + 80H and 81H. There is no CHS translation. INT 13H AH=08H + returns the P-CHS. The FDPT should contain the same P-CHS. + + Description: Supports up to 528MB from a table of drive + descriptions in BIOS ROM. No support for >1024 cylinders or + drives >528MB or LBA. + + Support issues: For >1024 cylinders or >528MB support, either + an option ROM with an INT 13H replacement (see BIOS types 4-7) + -or- a software driver (see BIOS type 8) must be added to the + system. + +BIOS Type 2 + + Origin: Unknown, but first appeared on systems having BIOS + drive type table entries defining >1024 cylinders. Rumored to + have originated at the request of Novell or SCO. + + BIOS call support: INT 13H AH=0xH and FDPT for BIOS drives + 80H and 81H. INT 13H AH=08H should return a L-CHS with the + cylinder value limited to 1024. Beware, many BIOS perform + a logical AND on the cylinder value. A correct BIOS will + limit the cylinder value as follows: + + cylinder = cylinder > 1024 ? 1024 : cylinder; + + An incorrect BIOS will limit the cylinder value as follows + (this implementation turns a 540MB drive into a 12MB drive!): + + cylinder = cylinder & 0x03ff; + + The FDPT will return a P-CHS that has the full cylinder + value. + + Description: For BIOS drive numbers 80H and 81H, this BIOS + type supports >1024 cylinders or >528MB without using a + translated CHS in the FDPT. INT 13H AH=08H truncates + cylinders to 1024 (beware of buggy implementations). The FDPT + can show >1024 cylinders thereby allowing an OS to support + drives >528MB. May convert the L-CHS or P-CHS directly to an + LBA if the ATA device supports LBA. + + Support issues: Actual support of >1024 cylinders is OS + specific -- some OS's may be able to place OS specific + partitions spanning or beyond cylinder 1024. Usually all OS + boot code must be within first 1024 cylinders. The FDISK + program of an OS that supports such partitions uses an OS + specific partition table entry format to identify these + paritions. There does not appear to be a standard (de facto + or otherwise) for this unusual partition table entry. + Apparently one method is to place -1 into the CHS fields and + use the LBA fields to describe the location of the partition. + This DOES NOT require the drive to support LBA addressing. + Using an LBA in the partition table entry is just a trick to + get around the CHS limits in the partition table entry. It is + unclear if such a partition table entry will be ignored by an + OS that does not understand what it is. For an OS that does + not support such partitions, either an option ROM with an INT + 13H replacement (see BIOS types 4-7) -or- a software driver + (see BIOS type 8) must be added to the system. + + Note: OS/2 can place HPFS partitions and Linux can place + Linux partitions beyond or spanning cylinder 1024. (Anyone + know of other systems that can do the same?) + +BIOS Type 3 + + Origin: Unknown, but first appeared on systems having BIOS + drive type table entires defining >1024 cylinders. Rumored to + have originated at the request of Novell or SCO. + + BIOS call support: INT 13H AH=0xH and FDPT for BIOS drives + 80H and 81H. INT 13H AH=08H can return an L-CHS with more + than 1024 cylinders. + + Description: This BIOS is like type 2 above but it allows up + to 4096 cylinders (12 cylinder bits). It does this in the INT + 13H AH=0xH calls by placing two most significant cylinder bits + (bits 11 and 10) into the upper two bits of the head number + (bits 7 and 6). + + Support issues: Identification of such a BIOS is difficult. + As long as the drive(s) supported by this type of BIOS have + <1024 cylinders this BIOS looks like a type 2 BIOS because INT + 13H AH=08H should return zero data in bits 7 and 6 of the head + information. If INT 13H AH=08H returns non zero data in bits + 7 and 6 of the head information, perhaps it can be assumed + that this is a type 3 BIOS. For more normal support of >1024 + cylinders or >528MB, either an option ROM with an INT 13H + replacement (see BIOS types 4-7) -or- a software driver (see + BIOS type 8) must be added to the system. + + Note: Apparently this BIOS type is no longer produced by any + BIOS vendor. + +BIOS Type 4 + + Origin: Compaq. Probably first appeared in systems with ESDI + drives having >1024 cylinders. + + BIOS call support: INT 13H AH=0xH and EDPT for BIOS drives + 80H and 81H. If the drive has <1024 cylinders, INT 13H AH=08H + returns the P-CHS and a FDPT is built. If the drive has >1024 + cylinders, INT 13H AH=08H returns an L-CHS and an EDPT is + built. + + Description: Looks like a type 2 BIOS when an FDPT is built. + Uses CHS translation when an EDPT is used. May convert the + L-CHS directly to an LBA if the ATA device supports LBA. + + Support issues: This BIOS type may support up to four drives + with a EDPT (or FDPT) for BIOS drive numbers 82H and 83H + located in memory following the EDPT (or FDPT) for drive 80H. + Different CHS translation algorithms may be used by the BIOS + and an OS. + +BIOS Type 5 + + Origin: The IBM/Microsoft BIOS Extensions document. For many + years this document was marked "confidential" so it did not + get wide spread distribution. + + BIOS call support: INT 13H AH=0xH, AH=4xH and EDPT for BIOS + drives 80H and 81H. INT 13H AH=08H returns an L-CHS. INT 13H + AH=41H and AH=48H should be used to get P-CHS configuration. + The FDPT/EDPT should not be used. In some implementations the + FDPT/EDPT may not exist. + + Description: A BIOS that supports very large drives (>1024 + cylinders, >528MB, actually >8GB), and supports the INT 13H + AH=4xH read/write functions. The AH=4xH calls use LBA + addressing and support drives with up to 2^64 sectors. These + calls do NOT require that a drive support LBA at the drive + interface. INT 13H AH=48H describes the L-CHS used at the INT + 13 interface and the P-CHS or LBA used at the drive interface. + This BIOS supports the INT 13 AH=0xH calls the same as a BIOS + type 4. + + Support issues: While the INT 13H AH=4xH calls are well + defined, they are not implemented in many systems shipping + today. Currently undefined is how such a BIOS should respond + to INT 13H AH=08H calls for a drive that is >8GB. Different + CHS translation algorithms may be used by the BIOS and an OS. + + Note: Support of LBA at the drive interface may be automatic + or may be under user control via a BIOS setup option. Use of + LBA at the drive interface does not change the operation of + the INT 13 interface. + +BIOS Type 6 + + Origin: The Phoenix Enhanced Disk Drive Specification. + + BIOS call support: INT 13H AH=0xH, AH=4xH and EDPT for BIOS + drives 80H and 81H. INT 13H AH=08H returns an L-CHS. INT 13H + AH=41H and AH=48H should be used to get P-CHS configuration. + INT 13H AH=48H returns the address of the Phoenix defined + "FDPT Extension" table. + + Description: A BIOS that supports very large drives (>1024 + cylinders, >528MB, actually >8GB), and supports the INT 13H + AH=4xH read/write functions. The AH=4xH calls use LBA + addressing and support drives with up to 2^64 sectors. These + calls do NOT require that a drive support LBA at the drive + interface. INT 13H AH=48H describes the L-CHS used at the INT + 13 interface and the P-CHS or LBA used at the drive interface. + This BIOS supports the INT 13 AH=0xH calls the same as a BIOS + type 4. The INT 13H AH=48H call returns additional information + such as host adapter addresses, DMA support, LBA support, etc, + in the Phoenix defined "FDPT Extension" table. + + Phoenix says this this BIOS need not support the INT 13H + AH=4xH read/write calls but this BIOS is really an + extension/enhancement of the original IBM/MS BIOS so most + implementations will probably support the full set of INT 13H + AH=4xH calls. + + Support issues: Currently undefined is how such a BIOS should + respond to INT 13H AH=08H calls for a drive that is >8GB. + Different CHS translation algorithms may be used by the BIOS + and an OS. + + Note: Support of LBA at the drive interface may be automatic + or may be under user control via a BIOS setup option. Use of + LBA at the drive interface does not change the operation of + the INT 13 interface. + +BIOS Type 7 + + Origin: Described in the Western Digital Enhanced IDE + Implementation Guide. + + BIOS call support: INT 13H AH=0xH and FDPT or EDPT for BIOS + drives 80H and 81H. An EDPT with a L-CHS of 16 heads and 63 + sectors is built when "LBA mode" is enabled. An FDPT is built + when "LBA mode" is disabled. + + Description: Supports >1024 cylinders or >528MB using a EDPT + with a translated CHS *** BUT ONLY IF *** the user requests + "LBA mode" in the BIOS setup *** AND *** the drive supports + LBA. As long as "LBA mode" is enabled, CHS translation is + enabled using a L-CHS with <=1024 cylinders, 16, 32, 64, ..., + heads and 63 sectors. Disk read/write commands are issued in + LBA mode at the ATA interface but other commands are issued in + P-CHS mode. Because the L-CHS is determined by table lookup + based on total drive capacity and not by a multiply/divide of + the P-CHS cylinder and head values, it may not be possible to + use the simple (and faster) bit shifting L-CHS to P-CHS + algorithms. + + When "LBA mode" is disabled, this BIOS looks like a BIOS type + 2 with an FDPT. The L-CHS used is taken either from the BIOS + drive type table or from the device's Identify Device data. + This L-CHS can be very different from the L-CHS returned when + "LBA mode" is enabled. + + This BIOS may support FDPT/EDPT for up to four drives in the + same manner as described in BIOS type 4. + + The basic problem with this BIOS is that the CHS returned by + INT 13H AH=08H changes because of a change in the "LBA mode" + setting in the BIOS setup. This should not happen. This use + or non-use of LBA at the ATA interface should have no effect + on the CHS returned by INT 13H AH=08H. This is the only BIOS + type know to have this problem. + + Support issues: If the user changes the "LBA mode" setting in + BIOS setup, INT 13H AH=08H and the FDPT/EDPT change + which may cause *** DATA CORRUPTION ***. The user should be + warned to not change the "LBA mode" setting in BIOS setup once + the drive has been partitioned and software installed. + Different CHS translation algorithms may be used by the BIOS + and an OS. + +BIOS Type 8 + + Origin: Unknown. Perhaps Ontrack's Disk Manager was the + first of these software drivers. Another example of such a + driver is Micro House's EZ Drive. + + BIOS call support: Unknown (anyone care to help out here?). + Mostly likely only INT 13H AH=0xH are support. Probably a + FDPT or EDPT exists for drives 80H and 81H. + +! Description: A software driver that "hides" in the MBR such + that it is loaded into system memory before any OS boot + processing starts. These drivers can have up to three parts: + a part that hides in the MBR, a part that hides in the + remaining sectors of cylinder 0, head 0, and an OS device + driver. The part in the MBR loads the second part of the + driver from cylinder 0 head 0. The second part provides a + replacement for INT 13H that enables CHS translation for at + least the boot drive. Usually the boot drive is defined in + CMOS setup as a type 1 or 2 (5MB or 10MB drive). Once the + second part of the driver is loaded, this definition is + changed to describe the true capacity of the drive and INT 13H + is replaced by the driver's version of INT 13H that does CHS + translation. In some cases the third part, an OS specific + device driver, must be loaded to enable CHS translation for + devices other than the boot device. + +! I don't know the details of how these drivers respond to INT + 13H AH=08H or how they set up drive parameter tables (anyone + care to help out here?). Some of these drivers convert the + L-CHS to an LBA, then they add a small number to the LBA and + finally they convert the LBA to a P-CHS. This in effect skips + over some sectors at the front of the disk. + + Support issues: Several identified -- Some OS installation + programs will remove or overlay these drivers; some of these + drivers do not perform CHS translation using the same + algorithms used by the other BIOS types; special OS device + drivers may be required in order to use these software drivers + For example, under MS Windows the standard FastDisk driver + (the 32-bit disk access driver) must be replaced by a driver + that understands the Ontrack, Micro House, etc, version of INT + 13H. Different CHS translation algorithms may be used by the + driver and an OS. + +! The hard disk vendors have been shipping these drivers with + their drives over 528MB during the last year and they have + been ignoring the statements of Microsoft and IBM that these + drivers would not be supported in future OS's. Now it appears + that both Microsoft and IBM are in a panic trying to figure + out how to support some of these drivers in WinNT, Win95 and + OS/2. It is unclear what the outcome of this will be at this + time. + +! NOTE: THIS IS NOT A PRODUCT ENDORSEMENT! An alternate + solution for an older ISA system is one of the BIOS + replacement cards. This cards have a BIOS option ROM. AMI + makes such a card called the "Disk Extender". This card + replaces the motherboard's INT 13H BIOS with a INT 13H BIOS + that does some form of CHS translation. Another solution for + older VL-Bus systems is an ATA-2 (EIDE) type host adapter card + that provides a option ROM with an INT 13H replacement. + +BIOS Type 9 + + Origin: SCSI host adapters. + + BIOS call support: Probably INT 13H AH=0xH and FDPT for BIOS + drives 80H and 81H, perhaps INT 13H AH=4xH. + + Description: Most SCSI host adapters contain an option ROM + that enables INT 13 support for the attached SCSI hard drives. + It is possible to have more than one SCSI host adapter, each + with its own option ROM. The CHS used at the INT 13H + interface is converted to the LBA that is used in the SCSI + commands. INT 13H AH=08H returns a CHS. This CHS will have + <=1024 cylinders, <=256 heads and <=63 sectors. The FDPT + probably will exist for SCSI drives with BIOS drive numbers of + 80H and 81H and probably indicates the same CHS as that + returned by INT 13H AH=08H. Even though the CHS used at the + INT 13H interface looks like a translated CHS, there is no + need to use a EDPT since there is no CHS-to-CHS translation + used. Other BIOS calls (most likely host adapter specific) + must be used to determine other information about the host + adapter or the drives. + + The INT 13H AH=4xH calls can be used to get beyond 8GB but + since there is little support for these calls in today's OS's, + there are probably few SCSI host adapters that support these + newer INT 13H calls. + + Support issues: Some SCSI host adapters will not install + their option ROM if there are two INT 13H devices previously + installed by another INT 13H BIOS (for example, two + MFM/RLL/ESDI/ATA drives). Other SCSI adapters will install + their option ROM and use BIOS drive numbers greater than 81H. + Some older OS's don't understand or use BIOS drive numbers + greater than 81H. SCSI adapters are currently faced with the + >8GB drive problem. + +BIOS Type 10 + + Origin: A european system vendor. + + BIOS call support: INT 13H AH=0xH and FDPT for BIOS drives + 80H and 81H. + + Description: This BIOS supports drives >528MB but it does not + support CHS translation. It supports only ATA drives with LBA + capability. INT 13H AH=08H returns an L-CHS. The L-CHS is + converted directly to an LBA. The BIOS sets the ATA drive to + a P-CHS of 16 heads and 63 sectors using the Initialize Drive + Parameters command but it does not use this P-CHS at the ATA + interface. + +! Support issues: OS/2 will probably work with this BIOS as + long as the drive's power on default P-CHS mode uses 16 heads + and 63 sectors. Because there is no EDPT, OS/2 uses the ATA + Identify Device power on default P-CHS, described in + Identify Device words 1, 3 and 6 as the current P-CHS for the + drive. However, this may not represent the correct P-CHS. A + newer drive will have the its current P-CHS information in + Identify Device words 53-58 but for some reason OS/2 does not + use this information. + +/end of part 2 of 2/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// diff --git a/etc/etc.i386/INSTALL.dbr b/etc/etc.i386/INSTALL.dbr new file mode 100644 index 00000000000..1f0b5fcefa8 --- /dev/null +++ b/etc/etc.i386/INSTALL.dbr @@ -0,0 +1,467 @@ + How It Works -- DOS Floppy Disk Boot Sector + + Version 1a + + by Hale Landis (landis@sugs.tware.com) + + +THE "HOW IT WORKS" SERIES + +This is one of several How It Works documents. The series +currently includes the following: + +* How It Works -- CHS Translation +* How It Works -- Master Boot Record +* How It Works -- DOS Floppy Boot Sector +* How It Works -- OS2 Boot Sector +* How It Works -- Partition Tables + + +DOS FLOPPY DISK BOOT SECTOR + +This article is a disassembly of a floppy disk boot sector for a +DOS floppy. The boot sector of a floppy disk is located at +cylinder 0, head 0, sector 1. This sector is created by a floppy +disk formating program, such as the DOS FORMAT program. The boot +sector of a FAT hard disk partition has a similar layout and +function. Basically a bootable FAT hard disk partition looks +like a big floppy during the early stages of the system's boot +processing. + +At the completion of your system's Power On Self Test (POST), INT +19 is called. Usually INT 19 tries to read a boot sector from +the first floppy drive. If a boot sector is found on the floppy +disk, the that boot sector is read into memory at location +0000:7C00 and INT 19 jumps to memory location 0000:7C00. +However, if no boot sector is found on the first floppy drive, +INT 19 tries to read the MBR from the first hard drive. If an +MBR is found it is read into memory at location 0000:7c00 and INT +19 jumps to memory location 0000:7c00. The small program in the +MBR will attempt to locate an active (bootable) partition in its +partition table. If such a partition is found, the boot sector +of that partition is read into memory at location 0000:7C00 and +the MBR program jumps to memory location 0000:7C00. Each +operating system has its own boot sector format. The small +program in the boot sector must locate the first part of the +operating system's kernel loader program (or perhaps the kernel +itself or perhaps a "boot manager program") and read that into +memory. + +INT 19 is also called when the CTRL-ALT-DEL keys are used. On +most systems, CTRL-ALT-DEL causes an short version of the POST to +be executed before INT 19 is called. + +===== + +Where stuff is: + + The BIOS Parameter Block (BPB) starts at offset 0. + The boot sector program starts at offset 3e. + The messages issued by this program start at offset 19e. + The DOS hidden file names start at offset 1e6. + The boot sector signature is at offset 1fe. + +Here is a summary of what this thing does: + +1) Copy Diskette Parameter Table which is pointed to by INT 1E. +2) Alter the copy of the Diskette Parameter Table. +3) Alter INT 1E to point to altered Diskette Parameter Table. +4) Do INT 13 AH=00, disk reset call. +5) Compute sector address of root directory. +6) Read first sector of root directory into 0000:0500. +7) Confirm that first two directory entries are for IO.SYS + and MSDOS.SYS. +8) Read first 3 sectors of IO.SYS into 0000:0700 (or 0070:0000). +9) Leave some information in the registers and jump to + IO.SYS at 0070:0000. + +NOTE: + + This program uses the CHS based INT 13H AH=02 to read the FAT + root directory and to read the IO.SYS file. If the drive is + >528MB, this CHS must be a translated CHS (or L-CHS, see my + BIOS TYPES document). Except for internal computations no + addresses in LBA form are used, another reason why LBA doesn't + solve the >528MB problem. + +===== + +Here is the entire sector in hex and ascii. + +OFFSET 0 1 2 3 4 5 6 7 8 9 A B C D E F *0123456789ABCDEF* +000000 eb3c904d 53444f53 352e3000 02010100 *.<.MSDOS5.0.....* +000010 02e00040 0bf00900 12000200 00000000 *...@............* +000020 00000000 0000295a 5418264e 4f204e41 *......)ZT.&NO NA* +000030 4d452020 20204641 54313220 2020fa33 *ME FAT12 .3* +000040 c08ed0bc 007c1607 bb780036 c5371e56 *.....|...x.6.7.V* +000050 1653bf3e 7cb90b00 fcf3a406 1fc645fe *.S.>|.........E.* +000060 0f8b0e18 7c884df9 894702c7 073e7cfb *....|.M..G...>|.* +000070 cd137279 33c03906 137c7408 8b0e137c *..ry3.9..|t....|* +000080 890e207c a0107cf7 26167c03 061c7c13 *.. |..|.&.|...|.* +000090 161e7c03 060e7c83 d200a350 7c891652 *..|...|....P|..R* +0000a0 7ca3497c 89164b7c b82000f7 26117c8b *|.I|..K|. ..&.|.* +0000b0 1e0b7c03 c348f7f3 0106497c 83164b7c *..|..H....I|..K|* +0000c0 00bb0005 8b16527c a1507ce8 9200721d *......R|.P|...r.* +0000d0 b001e8ac 0072168b fbb90b00 bee67df3 *.....r........}.* +0000e0 a6750a8d 7f20b90b 00f3a674 18be9e7d *.u... .....t...}* +0000f0 e85f0033 c0cd165e 1f8f048f 4402cd19 *._.3...^....D...* +000100 585858eb e88b471a 48488a1e 0d7c32ff *XXX...G.HH...|2.* +000110 f7e30306 497c1316 4b7cbb00 07b90300 *....I|..K|......* +000120 505251e8 3a0072d8 b001e854 00595a58 *PRQ.:.r....T.YZX* +000130 72bb0501 0083d200 031e0b7c e2e28a2e *r..........|....* +000140 157c8a16 247c8b1e 497ca14b 7cea0000 *.|..$|..I|.K|...* +000150 7000ac0a c07429b4 0ebb0700 cd10ebf2 *p....t).........* +000160 3b16187c 7319f736 187cfec2 88164f7c *;..|s..6.|....O|* +000170 33d2f736 1a7c8816 257ca34d 7cf8c3f9 *3..6.|..%|.M|...* +000180 c3b4028b 164d7cb1 06d2e60a 364f7c8b *.....M|.....6O|.* +000190 ca86e98a 16247c8a 36257ccd 13c30d0a *.....$|.6%|.....* +0001a0 4e6f6e2d 53797374 656d2064 69736b20 *Non-System disk * +0001b0 6f722064 69736b20 6572726f 720d0a52 *or disk error..R* +0001c0 65706c61 63652061 6e642070 72657373 *eplace and press* +0001d0 20616e79 206b6579 20776865 6e207265 * any key when re* +0001e0 6164790d 0a00494f 20202020 20205359 *ady...IO SY* +0001f0 534d5344 4f532020 20535953 000055aa *SMSDOS SYS..U.* + +===== + +The first 62 bytes of a boot sector are known as the BIOS +Parameter Block (BPB). Here is the layout of the BPB fields +and the values they are assigned in this boot sector: + + db JMP instruction at 7c00 size 2 = eb3c + db NOP instruction 7c02 1 90 + db OEMname 7c03 8 'MSDOS5.0' + dw bytesPerSector 7c0b 2 0200 + db sectPerCluster 7c0d 1 01 + dw reservedSectors 7c0e 2 0001 + db numFAT 7c10 1 02 + dw numRootDirEntries 7c11 2 00e0 + dw numSectors 7c13 2 0b40 (ignore numSectorsHuge) + db mediaType 7c15 1 f0 + dw numFATsectors 7c16 2 0009 + dw sectorsPerTrack 7c18 2 0012 + dw numHeads 7c1a 2 0002 + dd numHiddenSectors 7c1c 4 00000000 + dd numSectorsHuge 7c20 4 00000000 + db driveNum 7c24 1 00 + db reserved 7c25 1 00 + db signature 7c26 1 29 + dd volumeID 7c27 4 5a541826 + db volumeLabel 7c2b 11 'NO NAME ' + db fileSysType 7c36 8 'FAT12 ' + +===== + +Here is the boot sector... + +The first 3 bytes of the BPB are JMP and NOP instructions. + +0000:7C00 EB3C JMP START +0000:7C02 90 NOP + +Here is the rest of the BPB. + +0000:7C00 ......4d 53444f53 352e3000 02010100 * MSDOS5.0.....* +0000:7C10 02e00040 0bf00900 12000200 00000000 *...@............* +0000:7C20 00000000 0000295a 5418264e 4f204e41 *......)ZT.&NO NA* +0000:7C30 4d452020 20204641 54313220 2020.... *ME FAT12 * + +Now pay attention here... + + The 11 bytes starting at 0000:7c3e are immediately overlaid by + information copied from another part of memory. That + information is the Diskette Parameter Table. This data is + pointed to by INT 1E. This data is: + + 7c3e = Step rate and head unload time. + 7c3f = Head load time and DMA mode flag. + 7c40 = Delay for motor turn off. + 7c41 = Bytes per sector. + 7c42 = Sectors per track. + 7c43 = Intersector gap length. + 7c44 = Data length. + 7c45 = Intersector gap length during format. + 7c46 = Format byte value. + 7c47 = Head settling time. + 7c48 = Delay until motor at normal speed. + + The 11 bytes starting at 0000:7c49 are also overlaid by the + following data: + + 7c49 - 7c4c = diskette sector address (as LBA) + of the data area. + 7c4d - 7c4e = cylinder number to read from. + 7c4f - 7c4f = sector number to read from. + 7c50 - 7c53 = diskette sector address (as LBA) + of the root directory. + + START: START OF BOOT SECTOR PROGRAM + +0000:7C3E FA CLI interrupts off +0000:7C3F 33C0 XOR AX,AX set AX to zero +0000:7C41 8ED0 MOV SS,AX SS is now zero +0000:7C43 BC007C MOV SP,7C00 SP is now 7c00 +0000:7C46 16 PUSH SS also set ES +0000:7C47 07 POP ES to zero + + The INT 1E vector is at 0000:0078. + Get the address that the vector points to + into the DS:SI registers. + +0000:7C48 BB7800 MOV BX,0078 BX is now 78 +0000:7C4B 36 SS: +0000:7C4C C537 LDS SI,[BX] DS:SI is now [0:78] +0000:7C4E 1E PUSH DS save DS:SI -- +0000:7C4F 56 PUSH SI saves param tbl addr +0000:7C50 16 PUSH SS save SS:BX -- +0000:7C51 53 PUSH BX saves INT 1E address + + Move the diskette param table to 0000:7c3e. + +0000:7C52 BF3E7C MOV DI,7C3E DI is address of START +0000:7C55 B90B00 MOV CX,000B count is 11 +0000:7C58 FC CLD clear direction +0000:7C59 F3 REPZ move the diskette param +0000:7C5A A4 MOVSB table to 0000:7c3e +0000:7C5B 06 PUSH ES also set DS +0000:7C5C 1F POP DS to zero + + Alter some of the diskette param table data. + +0000:7C5D C645FE0F MOV BYTE PTR [DI-02],0F change head settle time + at 0000:7c47 +0000:7C61 8B0E187C MOV CX,[7C18] sectors per track +0000:7C65 884DF9 MOV [DI-07],CL save at 0000:7c42 + + Change INT 1E so that it points to the + altered Diskette param table at 0000:7c3e. + +0000:7C68 894702 MOV [BX+02],AX change INT 1E segment +0000:7C6B C7073E7C MOV WORD PTR [BX],7C3E change INT 1E offset + + Call INT 13 with AX=0000, disk reset, so + that the new diskette param table is used. + +0000:7C6F FB STI interrupts on +0000:7C70 CD13 INT 13 do diskette reset call +0000:7C72 7279 JB TALK jmp if any error + + Detemine the starting sector address of + the root directory as an LBA. + +0000:7C74 33C0 XOR AX,AX AX is now zero +0000:7C76 3906137C CMP [7C13],AX number sectros zero? +0000:7C7A 7408 JZ SMALL_DISK yes +0000:7C7C 8B0E137C MOV CX,[7C13] number of sectors +0000:7C80 890E207C MOV [7C20],CX save in huge num sects + + SMALL_DISK: + +0000:7C84 A0107C MOV AL,[7C10] number of FAT tables +0000:7C87 F726167C MUL WORD PTR [7C16] number of fat sectors +0000:7C8B 03061C7C ADD AX,[7C1C] number of hidden sectors +0000:7C8F 13161E7C ADC DX,[7C1E] number of hidden sectors +0000:7C93 03060E7C ADD AX,[7C0E] number of reserved sectors +0000:7C97 83D200 ADC DX,+00 number of reserved sectors +0000:7C9A A3507C MOV [7C50],AX save start addr +0000:7C9D 8916527C MOV [7C52],DX of root dir (as LBA) +0000:7CA1 A3497C MOV [7C49],AX save start addr +0000:7CA4 89164B7C MOV [7C4B],DX of root dir (as LBA) + + Determine sector address of first sector + in the data area as an LBA. + +0000:7CA8 B82000 MOV AX,0020 size of a dir entry (32) +0000:7CAB F726117C MUL WORD PTR [7C11] number of root dir entries +0000:7CAF 8B1E0B7C MOV BX,[7C0B] bytes per sector +0000:7CB3 03C3 ADD AX,BX +0000:7CB5 48 DEC AX +0000:7CB6 F7F3 DIV BX +0000:7CB8 0106497C ADD [7C49],AX add to start addr +0000:7CBC 83164B7C00 ADC WORD PTR [7C4B],+00 of root dir (as LBA) + + Read the first root dir sector into 0000:0500. + +0000:7CC1 BB0005 MOV BX,0500 addr to read into +0000:7CC4 8B16527C MOV DX,[7C52] get start of address +0000:7CC8 A1507C MOV AX,[7C50] of root dir (as LBA) +0000:7CCB E89200 CALL CONVERT call conversion routine +0000:7CCE 721D JB TALK jmp is any error +0000:7CD0 B001 MOV AL,01 read 1 sector +0000:7CD2 E8AC00 CALL READ_SECTORS read 1st root dir sector +0000:7CD5 7216 JB TALK jmp if any error +0000:7CD7 8BFB MOV DI,BX addr of 1st dir entry +0000:7CD9 B90B00 MOV CX,000B count is 11 +0000:7CDC BEE67D MOV SI,7DE6 addr of file names +0000:7CDF F3 REPZ is this "IO.SYS"? +0000:7CE0 A6 CMPSB +0000:7CE1 750A JNZ TALK no +0000:7CE3 8D7F20 LEA DI,[BX+20] addr of next dir entry +0000:7CE6 B90B00 MOV CX,000B count is 11 +0000:7CE9 F3 REPZ is this "MSDOS.SYS"? +0000:7CEA A6 CMPSB +0000:7CEB 7418 JZ FOUND_FILES they are equal + + TALK: + + Display "Non-System disk..." message, + wait for user to hit a key, restore + the INT 1E vector and then + call INT 19 to start boot processing + all over again. + +0000:7CED BE9E7D MOV SI,7D9E "Non-System disk..." +0000:7CF0 E85F00 CALL MSG_LOOP display message +0000:7CF3 33C0 XOR AX,AX INT 16 function +0000:7CF5 CD16 INT 16 read keyboard +0000:7CF7 5E POP SI get INT 1E vector's +0000:7CF8 1F POP DS address +0000:7CF9 8F04 POP [SI] restore the INT 1E +0000:7CFB 8F4402 POP [SI+02] vector's data +0000:7CFE CD19 INT 19 CALL INT 19 to try again + + SETUP_TALK: + +0000:7D00 58 POP AX pop junk off stack +0000:7D01 58 POP AX pop junk off stack +0000:7D02 58 POP AX pop junk off stack +0000:7D03 EBE8 JMP TALK now talk to the user + + FOUND_FILES: + + Compute the sector address of the first + sector of IO.SYS. + +0000:7D05 8B471A MOV AX,[BX+1A] get starting cluster num +0000:7D08 48 DEC AX subtract 1 +0000:7D09 48 DEC AX subtract 1 +0000:7D0A 8A1E0D7C MOV BL,[7C0D] sectors per cluster +0000:7D0E 32FF XOR BH,BH +0000:7D10 F7E3 MUL BX multiply +0000:7D12 0306497C ADD AX,[7C49] add start addr of +0000:7D16 13164B7C ADC DX,[7C4B] root dir (as LBA) + + Read IO.SYS into memory at 0000:0700. IO.SYS + is 3 sectors long. + +0000:7D1A BB0007 MOV BX,0700 address to read into +0000:7D1D B90300 MOV CX,0003 read 3 sectors + + READ_LOOP: + + Read the first 3 sectors of IO.SYS + (IO.SYS is much longer than 3 sectors). + +0000:7D20 50 PUSH AX save AX +0000:7D21 52 PUSH DX save DX +0000:7D22 51 PUSH CX save CX +0000:7D23 E83A00 CALL CONVERT call conversion routine +0000:7D26 72D8 JB SETUP_TALK jmp if error +0000:7D28 B001 MOV AL,01 read one sector +0000:7D2A E85400 CALL READ_SECTORS read one sector +0000:7D2D 59 POP CX restore CX +0000:7D2E 5A POP DX restore DX +0000:7D2F 58 POP AX restore AX +0000:7D30 72BB JB TALK jmp if any INT 13 error +0000:7D32 050100 ADD AX,0001 add one to the sector addr +0000:7D35 83D200 ADC DX,+00 add one to the sector addr +0000:7D38 031E0B7C ADD BX,[7C0B] incr mem addr by sect size +0000:7D3C E2E2 LOOP READ_LOOP read next sector + + Leave information in the AX, BX, CX and DX + registers for IO.SYS to use. Finally, + jump to IO.SYS at 0070:0000. + +0000:7D3E 8A2E157C MOV CH,[7C15] media type +0000:7D42 8A16247C MOV DL,[7C24] drive number +0000:7D46 8B1E497C MOV BX,[7C49] get start addr of +0000:7D4A A14B7C MOV AX,[7C4B] root dir (as LBA) +0000:7D4D EA00007000 JMP 0070:0000 JUMP TO 0070:0000 + + MSG_LOOP: + + This routine displays a message using + INT 10 one character at a time. + The message address is in DS:SI. + +0000:7D52 AC LODSB get message character +0000:7D53 0AC0 OR AL,AL end of message? +0000:7D55 7429 JZ RETURN jmp if yes +0000:7D57 B40E MOV AH,0E display one character +0000:7D59 BB0700 MOV BX,0007 video attrbiutes +0000:7D5C CD10 INT 10 display one character +0000:7D5E EBF2 JMP MSG_LOOP do again + + CONVERT: + This routine + converts a sector address (an LBA) to + a CHS address. The LBA is in DX:AX. + +0000:7D60 3B16187C CMP DX,[7C18] hi part of LBA > sectPerTrk? +0000:7D64 7319 JNB SET_CARRY jmp if yes +0000:7D66 F736187C DIV WORD PTR [7C18] div by sectors per track +0000:7D6A FEC2 INC DL add 1 to sector number +0000:7D6C 88164F7C MOV [7C4F],DL save sector number +0000:7D70 33D2 XOR DX,DX zero DX +0000:7D72 F7361A7C DIV WORD PTR [7C1A] div number of heads +0000:7D76 8816257C MOV [7C25],DL save head number +0000:7D7A A34D7C MOV [7C4D],AX save cylinder number +0000:7D7D F8 CLC clear carry +0000:7D7E C3 RET return + + SET_CARRY: + +0000:7D7F F9 STC set carry + + RETURN: + +0000:7D80 C3 RET return + + READ_SECTORS: + + The caller of this routine supplies: + AL = number of sectors to read + ES:BX = memory location to read into + and CHS address to read from in + memory locations 7c25 and 7C4d-7c4f. + +0000:7D81 B402 MOV AH,02 INT 13 read sectors +0000:7D83 8B164D7C MOV DX,[7C4D] get cylinder number +0000:7D87 B106 MOV CL,06 shift count +0000:7D89 D2E6 SHL DH,CL shift upper cyl left 6 bits +0000:7D8B 0A364F7C OR DH,[7C4F] or in sector number +0000:7D8F 8BCA MOV CX,DX move to CX +0000:7D91 86E9 XCHG CH,CL CH=cyl lo, CL=cyl hi + sect +0000:7D93 8A16247C MOV DL,[7C24] drive number +0000:7D97 8A36257C MOV DH,[7C25] head number +0000:7D9B CD13 INT 13 read sectors +0000:7D9D C3 RET return + +Data not used. + +0000:7D90 ca86e98a 16247c8a 36257ccd 13c3.... *.....$|.6%|... * + +Messages here. + +0000:7D90 ........ ........ ........ ....0d0a * ..* +0000:7Da0 4e6f6e2d 53797374 656d2064 69736b20 *Non-System disk * +0000:7Db0 6f722064 69736b20 6572726f 720d0a52 *or disk error..R* +0000:7Dc0 65706c61 63652061 6e642070 72657373 *eplace and press* +0000:7Dd0 20616e79 206b6579 20776865 6e207265 * any key when re* +0000:7De0 6164790d 0a00.... ........ ........ *ady... * + +MS DOS hidden file names (first two root directory entries). + +0000:7De0 ........ ....494f 20202020 20205359 * IO SY* +0000:7Df0 534d5344 4f532020 20535953 000055aa *SMSDOS SYS..U.* + +The last two bytes contain a 55AAH signature. + +0000:7Df0 ........ ........ ........ ....55aa * U.* + +/end/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// diff --git a/etc/etc.i386/INSTALL.mbr b/etc/etc.i386/INSTALL.mbr new file mode 100644 index 00000000000..6dcd856d154 --- /dev/null +++ b/etc/etc.i386/INSTALL.mbr @@ -0,0 +1,271 @@ + How It Works -- Master Boot Record + + Version 1a + + by Hale Landis (landis@sugs.tware.com) + + +THE "HOW IT WORKS" SERIES + +This is one of several How It Works documents. The series +currently includes the following: + +* How It Works -- CHS Translation +* How It Works -- Master Boot Record +* How It Works -- DOS Floppy Boot Sector +* How It Works -- OS2 Boot Sector +* How It Works -- Partition Tables + + +MASTER BOOT RECORD + +This article is a disassembly of a Master Boot Record (MBR). The +MBR is the sector at cylinder 0, head 0, sector 1 of a hard disk. +An MBR is created by the FDISK program. The FDISK program of all +operating systems must create a functionally similar MBR. The MBR +is first of what could be many partition sectors, each one +containing a four entry partition table. + +At the completion of your system's Power On Self Test (POST), INT +19 is called. Usually INT 19 tries to read a boot sector from +the first floppy drive. If a boot sector is found on the floppy +disk, the that boot sector is read into memory at location +0000:7C00 and INT 19 jumps to memory location 0000:7C00. +However, if no boot sector is found on the first floppy drive, +INT 19 tries to read the MBR from the first hard drive. If an +MBR is found it is read into memory at location 0000:7c00 and INT +19 jumps to memory location 0000:7c00. The small program in the +MBR will attempt to locate an active (bootable) partition in its +partition table. If such a partition is found, the boot sector +of that partition is read into memory at location 0000:7C00 and +the MBR program jumps to memory location 0000:7C00. Each +operating system has its own boot sector format. The small +program in the boot sector must locate the first part of the +operating system's kernel loader program (or perhaps the kernel +itself or perhaps a "boot manager program") and read that into +memory. + +INT 19 is also called when the CTRL-ALT-DEL keys are used. On +most systems, CTRL-ALT-DEL causes an short version of the POST to +be executed before INT 19 is called. + +===== + +Where stuff is: + + The MBR program code starts at offset 0000. + The MBR messages start at offset 008b. + The partition table starts at offset 00be. + The signature is at offset 00fe. + +Here is a summary of what this thing does: + + If an active partition is found, that partition's boot record + is read into 0000:7c00 and the MBR code jumps to 0000:7c00 + with SI pointing to the partition table entry that describes + the partition being booted. The boot record program uses this + data to determine the drive being booted from and the location + of the partition on the disk. + + If no active partition table enty is found, ROM BASIC is + entered via INT 18. All other errors cause a system hang, see + label HANG. + +NOTES (VERY IMPORTANT): + + 1) The first byte of an active partition table entry is 80. + This byte is loaded into the DL register before INT 13 is + called to read the boot sector. When INT 13 is called, DL is + the BIOS device number. Because of this, the boot sector read + by this MBR program can only be read from BIOS device number + 80 (the first hard disk). This is one of the reasons why it + is usually not possible to boot from any other hard disk. + + 2) The MBR program uses the CHS based INT 13H AH=02H call to + read the boot sector of the active partition. The location of + the active partition's boot sector is in the partition table + entry in CHS format. If the drive is >528MB, this CHS must be + a translated CHS (or L-CHS, see my BIOS TYPES document). + No addresses in LBA form are used (another reason why LBA + doesn't solve the >528MB problem). + +===== + +Here is the entire MBR record (hex dump and ascii). + +OFFSET 0 1 2 3 4 5 6 7 8 9 A B C D E F *0123456789ABCDEF* +000000 fa33c08e d0bc007c 8bf45007 501ffbfc *.3.....|..P.P...* +000010 bf0006b9 0001f2a5 ea1d0600 00bebe07 *................* +000020 b304803c 80740e80 3c00751c 83c610fe *...<.t..<.u.....* +000030 cb75efcd 188b148b 4c028bee 83c610fe *.u......L.......* +000040 cb741a80 3c0074f4 be8b06ac 3c00740b *.t..<.t.....<.t.* +000050 56bb0700 b40ecd10 5eebf0eb febf0500 *V.......^.......* +000060 bb007cb8 010257cd 135f730c 33c0cd13 *..|...W.._s.3...* +000070 4f75edbe a306ebd3 bec206bf fe7d813d *Ou...........}.=* +000080 55aa75c7 8bf5ea00 7c000049 6e76616c *U.u.....|..Inval* +000090 69642070 61727469 74696f6e 20746162 *id partition tab* +0000a0 6c650045 72726f72 206c6f61 64696e67 *le.Error loading* +0000b0 206f7065 72617469 6e672073 79737465 * operating syste* +0000c0 6d004d69 7373696e 67206f70 65726174 *m.Missing operat* +0000d0 696e6720 73797374 656d0000 00000000 *ing system......* +0000e0 00000000 00000000 00000000 00000000 *................* +0000f0 TO 0001af SAME AS ABOVE +0001b0 00000000 00000000 00000000 00008001 *................* +0001c0 0100060d fef83e00 00000678 0d000000 *......>....x....* +0001d0 00000000 00000000 00000000 00000000 *................* +0001e0 00000000 00000000 00000000 00000000 *................* +0001f0 00000000 00000000 00000000 000055aa *..............U.* + +===== + +Here is the disassembly of the MBR... + +This sector is initially loaded into memory at 0000:7c00 but +it immediately relocates itself to 0000:0600. + + BEGIN: NOW AT 0000:7C00, RELOCATE + +0000:7C00 FA CLI disable int's +0000:7C01 33C0 XOR AX,AX set stack seg to 0000 +0000:7C03 8ED0 MOV SS,AX +0000:7C05 BC007C MOV SP,7C00 set stack ptr to 7c00 +0000:7C08 8BF4 MOV SI,SP SI now 7c00 +0000:7C0A 50 PUSH AX +0000:7C0B 07 POP ES ES now 0000:7c00 +0000:7C0C 50 PUSH AX +0000:7C0D 1F POP DS DS now 0000:7c00 +0000:7C0E FB STI allow int's +0000:7C0F FC CLD clear direction +0000:7C10 BF0006 MOV DI,0600 DI now 0600 +0000:7C13 B90001 MOV CX,0100 move 256 words (512 bytes) +0000:7C16 F2 REPNZ move MBR from 0000:7c00 +0000:7C17 A5 MOVSW to 0000:0600 +0000:7C18 EA1D060000 JMP 0000:061D jmp to NEW_LOCATION + + NEW_LOCATION: NOW AT 0000:0600 + +0000:061D BEBE07 MOV SI,07BE point to first table entry +0000:0620 B304 MOV BL,04 there are 4 table entries + + SEARCH_LOOP1: SEARCH FOR AN ACTIVE ENTRY + +0000:0622 803C80 CMP BYTE PTR [SI],80 is this the active entry? +0000:0625 740E JZ FOUND_ACTIVE yes +0000:0627 803C00 CMP BYTE PTR [SI],00 is this an inactive entry? +0000:062A 751C JNZ NOT_ACTIVE no +0000:062C 83C610 ADD SI,+10 incr table ptr by 16 +0000:062F FECB DEC BL decr count +0000:0631 75EF JNZ SEARCH_LOOP1 jmp if not end of table +0000:0633 CD18 INT 18 GO TO ROM BASIC + + FOUND_ACTIVE: FOUND THE ACTIVE ENTRY + +0000:0635 8B14 MOV DX,[SI] set DH/DL for INT 13 call +0000:0637 8B4C02 MOV CX,[SI+02] set CH/CL for INT 13 call +0000:063A 8BEE MOV BP,SI save table ptr + + SEARCH_LOOP2: MAKE SURE ONLY ONE ACTIVE ENTRY + +0000:063C 83C610 ADD SI,+10 incr table ptr by 16 +0000:063F FECB DEC BL decr count +0000:0641 741A JZ READ_BOOT jmp if end of table +0000:0643 803C00 CMP BYTE PTR [SI],00 is this an inactive entry? +0000:0646 74F4 JZ SEARCH_LOOP2 yes + + NOT_ACTIVE: MORE THAN ONE ACTIVE ENTRY FOUND + +0000:0648 BE8B06 MOV SI,068B display "Invld prttn tbl" + + DISPLAY_MSG: DISPLAY MESSAGE LOOP + +0000:064B AC LODSB get char of message +0000:064C 3C00 CMP AL,00 end of message +0000:064E 740B JZ HANG yes +0000:0650 56 PUSH SI save SI +0000:0651 BB0700 MOV BX,0007 screen attributes +0000:0654 B40E MOV AH,0E output 1 char of message +0000:0656 CD10 INT 10 to the display +0000:0658 5E POP SI restore SI +0000:0659 EBF0 JMP DISPLAY_MSG do it again + + HANG: HANG THE SYSTEM LOOP + +0000:065B EBFE JMP HANG sit and stay! + + READ_BOOT: READ ACTIVE PARITION BOOT RECORD + +0000:065D BF0500 MOV DI,0005 INT 13 retry count + + INT13RTRY: INT 13 RETRY LOOP + +0000:0660 BB007C MOV BX,7C00 +0000:0663 B80102 MOV AX,0201 read 1 sector +0000:0666 57 PUSH DI save DI +0000:0667 CD13 INT 13 read sector into 0000:7c00 +0000:0669 5F POP DI restore DI +0000:066A 730C JNB INT13OK jmp if no INT 13 +0000:066C 33C0 XOR AX,AX call INT 13 and +0000:066E CD13 INT 13 do disk reset +0000:0670 4F DEC DI decr DI +0000:0671 75ED JNZ INT13RTRY if not zero, try again +0000:0673 BEA306 MOV SI,06A3 display "Errr ldng systm" +0000:0676 EBD3 JMP DISPLAY_MSG jmp to display loop + + INT13OK: INT 13 ERROR + +0000:0678 BEC206 MOV SI,06C2 "missing op sys" +0000:067B BFFE7D MOV DI,7DFE point to signature +0000:067E 813D55AA CMP WORD PTR [DI],AA55 is signature correct? +0000:0682 75C7 JNZ DISPLAY_MSG no +0000:0684 8BF5 MOV SI,BP set SI +0000:0686 EA007C0000 JMP 0000:7C00 JUMP TO THE BOOT SECTOR + WITH SI POINTING TO + PART TABLE ENTRY + +Messages here. + +0000:0680 ........ ........ ......49 6e76616c * Inval* +0000:0690 69642070 61727469 74696f6e 20746162 *id partition tab* +0000:06a0 6c650045 72726f72 206c6f61 64696e67 *le.Error loading* +0000:06b0 206f7065 72617469 6e672073 79737465 * operating syste* +0000:06c0 6d004d69 7373696e 67206f70 65726174 *m.Missing operat* +0000:06d0 696e6720 73797374 656d00.. ........ *ing system. * + +Data not used. + +0000:06d0 ........ ........ ......00 00000000 * .....* +0000:06e0 00000000 00000000 00000000 00000000 *................* +0000:06f0 00000000 00000000 00000000 00000000 *................* +0000:0700 00000000 00000000 00000000 00000000 *................* +0000:0710 00000000 00000000 00000000 00000000 *................* +0000:0720 00000000 00000000 00000000 00000000 *................* +0000:0730 00000000 00000000 00000000 00000000 *................* +0000:0740 00000000 00000000 00000000 00000000 *................* +0000:0750 00000000 00000000 00000000 00000000 *................* +0000:0760 00000000 00000000 00000000 00000000 *................* +0000:0770 00000000 00000000 00000000 00000000 *................* +0000:0780 00000000 00000000 00000000 00000000 *................* +0000:0790 00000000 00000000 00000000 00000000 *................* +0000:07a0 00000000 00000000 00000000 00000000 *................* +0000:07b0 00000000 00000000 00000000 0000.... *............ * + +The partition table starts at 0000:07be. Each partition table +entry is 16 bytes. This table defines a single primary partition +which is also an active (bootable) partition. + +0000:07b0 ........ ........ ........ ....8001 * ....* +0000:07c0 0100060d fef83e00 00000678 0d000000 *......>....x....* +0000:07d0 00000000 00000000 00000000 00000000 *................* +0000:07e0 00000000 00000000 00000000 00000000 *................* +0000:07f0 00000000 00000000 00000000 0000.... *............ * + +The last two bytes contain a 55AAH signature. + +0000:07f0 ........ ........ ........ ....55aa *..............U.* + +/end/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// diff --git a/etc/etc.i386/INSTALL.os2br b/etc/etc.i386/INSTALL.os2br new file mode 100644 index 00000000000..6f243869484 --- /dev/null +++ b/etc/etc.i386/INSTALL.os2br @@ -0,0 +1,469 @@ + How It Works -- OS2 Boot Sector + + Version 1a + + by Hale Landis (landis@sugs.tware.com) + + +THE "HOW IT WORKS" SERIES + +This is one of several How It Works documents. The series +currently includes the following: + +* How It Works -- CHS Translation +* How It Works -- Master Boot Record +* How It Works -- DOS Floppy Boot Sector +* How It Works -- OS2 Boot Sector +* How It Works -- Partition Tables + + +OS2 BOOT SECTOR + +Note: I'll leave it to someone else to provide you with a +disassembly of an OS/2 HPFS boot sector, or a Linux boot sector, +or a WinNT boot sector, etc. + +This article is a disassembly of a floppy or hard disk boot +sector for OS/2. Apparently OS/2 uses the same boot sector for +both environments. Basically a bootable FAT hard disk partition +looks like a big floppy during the early stages of the system's +boot processing. This sector is at cylinder 0, head 0, sector 1 +of a floppy or it is the first sector within a FAT hard disk +partition. OS/2 floppy disk and hard disk boot sectors are +created by the OS/2 FORMAT program. + +At the completion of your system's Power On Self Test (POST), INT +19 is called. Usually INT 19 tries to read a boot sector from +the first floppy drive. If a boot sector is found on the floppy +disk, the that boot sector is read into memory at location +0000:7C00 and INT 19 jumps to memory location 0000:7C00. +However, if no boot sector is found on the first floppy drive, +INT 19 tries to read the MBR from the first hard drive. If an +MBR is found it is read into memory at location 0000:7c00 and INT +19 jumps to memory location 0000:7c00. The small program in the +MBR will attempt to locate an active (bootable) partition in its +partition table. If such a partition is found, the boot sector +of that partition is read into memory at location 0000:7C00 and +the MBR program jumps to memory location 0000:7C00. Each +operating system has its own boot sector format. The small +program in the boot sector must locate the first part of the +operating system's kernel loader program (or perhaps the kernel +itself or perhaps a "boot manager program") and read that into +memory. + +INT 19 is also called when the CTRL-ALT-DEL keys are used. On +most systems, CTRL-ALT-DEL causes an short version of the POST to +be executed before INT 19 is called. + +===== + +Where stuff is: + + The BIOS Parameter Block (BPB) starts at offset 0. + The boot sector program starts at offset 46. + The messages issued by this program start at offset 198. + The OS/2 boot loader file name starts at offset 1d5. + The boot sector signature is at offset 1fe. + +Here is a summary of what this thing does: + + 1) If booting from a hard disk partition, skip to step 6. + 2) Copy Diskette Parameter Table which is pointed to by INT 1E + to the top of memory. + 3) Alter the copy of the Diskette Parameter Table. + 4) Alter INT 1E to point to altered Diskette Parameter Table at + the top of memory. + 5) Do INT 13 AH=00, disk reset call so that the altered + Diskette Parameter Table is used. + 6) Compute sector address of the root directory. + 7) Read the entire root directory into memory starting at + location 1000:0000. + 8) Search the root directory entires for the file OS2BOOT. + 9) Read the OS2BOOT file into memory at 0800:0000. +10) Do a far return to enter the OS2BOOT program at 0800:0000. + +NOTES: + + This program uses the CHS based INT 13H AH=02 to read the FAT + root directory and to read the OS2BOOT file. If the drive is + >528MB, this CHS must be a translated CHS (or L-CHS, see my + BIOS TYPES document). Except for internal computations no + addresses in LBA form are used, another reason why LBA doesn't + solve the >528MB problem. + +===== + +Here is the entire sector in hex and ascii. + +OFFSET 0 1 2 3 4 5 6 7 8 9 A B C D E F *0123456789ABCDEF* +000000 eb449049 424d2032 302e3000 02100100 *.D.IBM 20.0.....* +000010 02000200 00f8d800 3e000e00 3e000000 *........>...>...* +000020 06780d00 80002900 1c0c234e 4f204e41 *.x....)...#NO NA* +000030 4d452020 20204641 54202020 20200000 *ME FAT ..* +000040 00100000 0000fa33 db8ed3bc ff7bfbba *.......3.....{..* +000050 c0078eda 803e2400 00753d1e b840008e *.....>$..u=..@..* +000060 c026ff0e 1300cd12 c1e0068e c033ff33 *.&...........3.3* +000070 c08ed8c5 367800fc b90b00f3 a41fa118 *....6x..........* +000080 0026a204 001e33c0 8ed8a378 008c067a *.&....3....x...z* +000090 001f8a16 2400cd13 a0100098 f7261600 *....$........&..* +0000a0 03060e00 5091b820 00f72611 008b1e0b *....P.. ..&.....* +0000b0 0003c348 f7f35003 c1a33e00 b800108e *...H..P...>.....* +0000c0 c033ff59 890e4400 58a34200 33d2e873 *.3.Y..D.X.B.3..s* +0000d0 0033db8b 0e11008b fb51b90b 00bed501 *.3.......Q......* +0000e0 f3a65974 0583c320 e2ede335 268b471c *..Yt... ...5&.G.* +0000f0 268b571e f7360b00 fec08ac8 268b571a *&.W..6......&.W.* +000100 4a4aa00d 0032e4f7 e203063e 0083d200 *JJ...2.....>....* +000110 bb00088e c333ff06 57e82800 8d360b00 *.....3..W.(..6..* +000120 cbbe9801 eb03bead 01e80900 bec201e8 *................* +000130 0300fbeb feac0ac0 7409b40e bb0700cd *........t.......* +000140 10ebf2c3 50525103 061c0013 161e00f7 *....PRQ.........* +000150 361800fe c28ada33 d2f7361a 008afa8b *6......3..6.....* +000160 d0a11800 2ac34050 b402b106 d2e60af3 *....*.@P........* +000170 8bca86e9 8a162400 8af78bdf cd1372a6 *......$.......r.* +000180 5b598bc3 f7260b00 03f85a58 03c383d2 *[Y...&....ZX....* +000190 002acb7f afc31200 4f532f32 20212120 *.*......OS/2 !! * +0001a0 53595330 31343735 0d0a0012 004f532f *SYS01475.....OS/* +0001b0 32202121 20535953 30323032 350d0a00 *2 !! SYS02025...* +0001c0 12004f53 2f322021 21205359 53303230 *..OS/2 !! SYS020* +0001d0 32370d0a 004f5332 424f4f54 20202020 *27...OS2BOOT * +0001e0 00000000 00000000 00000000 00000000 *................* +0001f0 00000000 00000000 00000000 000055aa *..............U.* + +===== + +The first 62 bytes of a boot sector are known as the BIOS +Parameter Block (BPB). Here is the layout of the BPB fields +and the values they are assigned in this boot sector: + + db JMP instruction at 7c00 size 2 = eb44 + db NOP instruction 7c02 1 90 + db OEMname 7c03 8 'IBM 20.0' + dw bytesPerSector 7c0b 2 0200 + db sectPerCluster 7c0d 1 01 + dw reservedSectors 7c0e 2 0001 + db numFAT 7c10 1 02 + dw numRootDirEntries 7c11 2 0200 + dw numSectors 7c13 2 0000 (use numSectorsHuge) + db mediaType 7c15 1 f8 + dw numFATsectors 7c16 2 00d8 + dw sectorsPerTrack 7c18 2 003e + dw numHeads 7c1a 2 000e + dd numHiddenSectors 7c1c 4 00000000 + dd numSectorsHuge 7c20 4 000d7806 + db driveNum 7c24 1 80 + db reserved 7c25 1 00 + db signature 7c26 1 29 + dd volumeID 7c27 4 001c0c23 + db volumeLabel 7c2b 11 'NO NAME ' + db fileSysType 7c36 8 'FAT ' + +===== + +Here is the boot sector... + +The first 3 bytes of the BPB are JMP and NOP instructions. + +0000:7C00 EB44 JMP START +0000:7C02 90 NOP + +Here is the rest of the BPB. + +0000:7C00 eb449049 424d2032 302e3000 02100100 *.D.IBM 20.0.....* +0000:7C10 02000200 00f8d800 3e000e00 3e000000 *........>...>...* +0000:7C20 06780d00 80002900 1c0c234e 4f204e41 *.x....)...#NO NA* +0000:7C30 4d452020 20204641 54202020 20200000 *ME FAT ..* + +Additional data areas. + +0000:7C30 ........ ........ ........ ....0000 * ..* +0000:7C40 00100000 0000.... ........ ........ *...... * + + Note: + + 0000:7c3e (DS:003e) = number of sectors in the FATs and root dir. + 0000:7c42 (DS:0042) = number of sectors in the FAT. + 0000:7c44 (DS:0044) = number of sectors in the root dir. + + START: START OF BOOT SECTOR PROGRAM + +0000:7C46 FA CLI interrupts off +0000:7C47 33DB XOR BX,BX zero BX +0000:7C49 8ED3 MOV SS,BX SS now zero +0000:7C4B BCFF7B MOV SP,7BFF SP now 7bff +0000:7C4E FB STI interrupts on +0000:7C4F BAC007 MOV DX,07C0 set DX to +0000:7C52 8EDA MOV DS,DX 07c0 + + Are we booting from a floppy or a + hard disk partition? + +0000:7C54 803E240000 CMP BYTE PTR [0024],00 is driveNum in BPB 00? +0000:7C59 753D JNZ NOT_FLOPPY jmp if not zero + + We are booting from a floppy. The + Diskette Parameter Table must be + copied and altered... + + Diskette Parameter Table is pointed to by INT 1E. This + program moves this table to high memory, alters the table, and + changes INT 1E to point to the altered table. + + This table contains the following data: + + ????:0000 = Step rate and head unload time. + ????:0001 = Head load time and DMA mode flag. + ????:0002 = Delay for motor turn off. + ????:0003 = Bytes per sector. + ????:0004 = Sectors per track. + ????:0005 = Intersector gap length. + ????:0006 = Data length. + ????:0007 = Intersector gap length during format. + ????:0008 = Format byte value. + ????:0009 = Head settling time. + ????:000a = Delay until motor at normal speed. + + Compute a valid high memory address. + +0000:7C5B 1E PUSH DS save DS +0000:7C5C B84000 MOV AX,0040 set ES +0000:7C5F 8EC0 MOV ES,AX to 0040 (BIOS data area) +0000:7C61 26 ES: reduce system memory +0000:7C62 FF0E1300 DEC WORD PTR [0013] size by 1024 +0000:7C66 CD12 INT 12 get system memory size +0000:7C68 C1E06 SHL AX,06 shift AX (mult by 64) +0000:7C6B 8EC0 MOV ES,AX move to ES +0000:7C6D 33FF XOR DI,DI zero DI + + Move the diskette param table to high memory. + +0000:7C6F 33C0 XOR AX,AX zero AX +0000:7C71 8ED8 MOV DS,AX DS now zero +0000:7C73 C5367800 LDS SI,[0078] DS:SI = INT 1E vector +0000:7C77 FC CLD clear direction +0000:7C78 B90B00 MOV CX,000B count is 11 +0000:7C7B F3 REPZ copy diskette param table +0000:7C7C A4 MOVSB to top of memory + + Alter the number of sectors per track + in the diskette param table in high memory. + +0000:7C7D 1F POP DS restore DS +0000:7C7E A11800 MOV AX,[0018] get sectorsPerTrack from BPB +0000:7C81 26 ES: alter sectors per track +0000:7C82 A20400 MOV [0004],AL in diskette param table + + Change INT 1E to point to altered diskette + param table and do a INT 13 disk reset call. + +0000:7C85 1E PUSH DS save DS +0000:7C86 33C0 XOR AX,AX AX now zero +0000:7C88 8ED8 MOV DS,AX DS no zero +0000:7C8A A37800 MOV [0078],AX alter INT 1E vector +0000:7C8D 8C067A00 MOV [007A],ES to point to altered + diskette param table +0000:7C91 1F POP DS restore DS +0000:7C92 8A162400 MOV DL,[0024] driveNum from BPB +0000:7C96 CD13 INT 13 diskette reset + + NOT_FLOPPY: + + Compute the location and the size of + the root directory. Read the entire + root directory into memory. + +0000:7C98 A01000 MOV AL,[0010] get numFAT +0000:7C9B 98 CBW make into a word +0000:7C9C F7261600 MUL WORD PTR [0016] mult by numFatSectors +0000:7CA0 03060E00 ADD AX,[000E] add reservedSectors +0000:7CA4 50 PUSH AX save +0000:7CA5 91 XCHG CX,AX move to CX +0000:7CA6 B82000 MOV AX,0020 dir entry size +0000:7CA9 F7261100 MUL WORD PTR [0011] mult by numRootDirEntries +0000:7CAD 8B1E0B00 MOV BX,[000B] get bytesPerSector +0000:7CB1 03C3 ADD AX,BX add +0000:7CB3 48 DEC AX subtract 1 +0000:7CB4 F7F3 DIV BX div by bytesPerSector +0000:7CB6 50 PUSH AX save number of dir sectors +0000:7CB7 03C1 ADD AX,CX add number of fat sectors +0000:7CB9 A33E00 MOV [003E],AX save +0000:7CBC B80010 MOV AX,1000 AX is now 1000 +0000:7CBF 8EC0 MOV ES,AX ES is now 1000 +0000:7CC1 33FF XOR DI,DI DI is now zero +0000:7CC3 59 POP CX get number dir sectors +0000:7CC4 890E4400 MOV [0044],CX save +0000:7CC8 58 POP AX get number fat sectors +0000:7CC9 A34200 MOV [0042],AX save +0000:7CCC 33D2 XOR DX,DX DX now zero +0000:7CCE E87300 CALL READ_SECTOR read 1st sect of root dir +0000:7CD1 33DB XOR BX,BX BX is now zero +0000:7CD3 8B0E1100 MOV CX,[0011] number of root dir entries + + DIR_SEARCH: SEARCH FOR OS2BOOT. + + Search the root directory for the file + name OS2BOOT. + +0000:7CD7 8BFB MOV DI,BX DI is dir entry addr +0000:7CD9 51 PUSH CX save CX +0000:7CDA B90B00 MOV CX,000B count is 11 +0000:7CDD BED501 MOV SI,01D5 addr of "OS2BOOT" +0000:7CE0 F3 REPZ is 1st dir entry +0000:7CE1 A6 CMPSB for "OS2BOOT"? +0000:7CE2 59 POP CX restore CX +0000:7CE3 7405 JZ FOUND_OS2BOOT jmp if OS2BOOT +0000:7CE5 83C320 ADD BX,+20 incr to next dir entry +0000:7CE8 E2ED LOOP DIR_SEARCH try again + + FOUND_OS2BOOT: FOUND OS2BOOT. + + OS2BOOT was found. Get the starting + cluster number and convert to a sector + address. Read OS2BOOT into memory and + finally do a far return to enter + the OS2BOOT program. + +0000:7CEA E335 JCXZ FAILED1 JMP if CX zero. +0000:7CEC 26 ES: get the szie of +0000:7CED 8B471C MOV AX,[BX+1C] the OS2BOOT file +0000:7CF0 26 ES: from the OS2BOOT +0000:7CF1 8B571E MOV DX,[BX+1E] directory entry +0000:7CF4 F7360B00 DIV WORD PTR [000B] div by bytesPerSect +0000:7CF8 FEC0 INC AL add 1 +0000:7CFA 8AC8 MOV CL,AL num sectors OS2BOOT +0000:7CFC 26 ES: get the starting +0000:7CFD 8B571A MOV DX,[BX+1A] cluster number +0000:7D00 4A DEC DX subtract 1 +0000:7D01 4A DEC DX subtract 1 +0000:7D02 A00D00 MOV AL,[000D] sectorsPerCluster +0000:7D05 32E4 XOR AH,AH mutiply +0000:7D07 F7E2 MUL DX to get LBA +0000:7D09 03063E00 ADD AX,[003E] add number of FAT sectors +0000:7D0D 83D200 ADC DX,+00 to LBA +0000:7D10 BB0008 MOV BX,0800 set ES +0000:7D13 8EC3 MOV ES,BX to 0800 +0000:7D15 33FF XOR DI,DI set ES:DI to entry point +0000:7D17 06 PUSH ES address of +0000:7D18 57 PUSH DI OS2BOOT +0000:7D19 E82800 CALL READ_SECTOR read OS2BOOT into memory +0000:7D1C 8D360B00 LEA SI,[000B] set DS:SI +0000:7D20 CB RETF "far return" to OS2BOOT + + FAILED1: OS2BOOT WAS NOT FOUND. + +0000:7D21 BE9801 MOV SI,0198 "SYS01475" message +0000:7D24 EB03 JMP FAILED3 + + FAILED2: ERROR FROM INT 13. + +0000:7D26 BEAD01 MOV SI,01AD "SYS02025" message + + FAILED3: OUTPUT ERROR MESSAGES. + +0000:7D29 E80900 CALL MSG_LOOP display message +0000:7D2C BEC201 MOV SI,01C2 "SYS02027" message +0000:7D2F E80300 CALL MSG_LOOP display message +0000:7D32 FB STI interrupts on + + HANG: HANG THE SYSTEM! + +0000:7D33 EBFE JMP HANG sit and stay! + + MSG_LOOP: DISPLAY AN ERROR MESSAGE. + + Routine to display the message + text pointed to by SI. + +0000:7D35 AC LODSB get next char of message +0000:7D36 0AC0 OR AL,AL end of message? +0000:7D38 7409 JZ RETURN jmp if yes +0000:7D3A B40E MOV AH,0E write 1 char +0000:7D3C BB0700 MOV BX,0007 video attributes +0000:7D3F CD10 INT 10 INT 10 to write 1 char +0000:7D41 EBF2 JMP MSG_LOOP do again + + RETURN: + +0000:7D43 C3 RET return + + READ_SECTOR: ROUTINE TO READ SECTORS. + + Read sectors into memory. Read multiple + sectors but don't read across a track + boundary. + + The caller supplies the following: + DX:AX = sector address to read (as LBA) + CX = number of sectors to read + ES:DI = memory address to read into + +0000:7D44 50 PUSH AX save lower part of LBA +0000:7D45 52 PUSH DX save upper part of LBA +0000:7D46 51 PUSH CX save number of sect to read +0000:7D47 03061C00 ADD AX,[001C] add numHiddenSectors +0000:7D4B 13161E00 ADC DX,[001E] to LBA +0000:7D4F F7361800 DIV WORD PTR [0018] div by sectorsPerTrack +0000:7D53 FEC2 INC DL add 1 to sector number +0000:7D55 8ADA MOV BL,DL save sector number +0000:7D57 33D2 XOR DX,DX zero upper part of LBA +0000:7D59 F7361A00 DIV WORD PTR [001A] div by numHeads +0000:7D5D 8AFA MOV BH,DL save head number +0000:7D5F 8BD0 MOV DX,AX save cylinder number +0000:7D61 A11800 MOV AX,[0018] sectorsPerTrack +0000:7D64 2AC3 SUB AL,BL sub sector number +0000:7D66 40 INC AX add 1 +0000:7D67 50 PUSH AX save number of sector to read +0000:7D68 B402 MOV AH,02 INT 13 read sectors +0000:7D6A B106 MOV CL,06 shift count +0000:7D6C D2E6 SHL DH,CL shift high cyl left +0000:7D6E 0AF3 OR DH,BL or in sector number +0000:7D70 8BCA MOV CX,DX move cyl/sect to CX +0000:7D72 86E9 XCHG CH,CL swap cyl/sect +0000:7D74 8A162400 MOV DL,[0024] driveNum +0000:7D78 8AF7 MOV DH,BH head number +0000:7D7A 8BDF MOV BX,DI memory addr to read into +0000:7D7C CD13 INT 13 INT 13 read sectors call +0000:7D7E 72A6 JB FAILED2 jmp if any error +0000:7D80 5B POP BX get number of sectors read +0000:7D81 59 POP CX restore CX +0000:7D82 8BC3 MOV AX,BX number of sector to AX +0000:7D84 F7260B00 MUL WORD PTR [000B] multiply by sector size +0000:7D88 03F8 ADD DI,AX add to memory address +0000:7D8A 5A POP DX restore upper part of LBA +0000:7D8B 58 POP AX resotre lower part of LBA +0000:7D8C 03C3 ADD AX,BX add number of sector just +0000:7D8E 83D200 ADC DX,+00 read to LBA +0000:7D91 2ACB SUB CL,BL decr requested num of sect +0000:7D93 7FAF JG READ_SECTOR jmp if not zero +0000:7D95 C3 RET return + +Data not used. + +0000:7D90 ........ ....1200 ........ ........ * .. * + +Messages here. + +0000:7D90 ........ ........ 4f532f32 20212120 * OS/2 !! * +0000:7Da0 53595330 31343735 0d0a0012 004f532f *SYS01475.....OS/* +0000:7Db0 32202121 20535953 30323032 350d0a00 *2 !! SYS02025...* +0000:7Dc0 12004f53 2f322021 21205359 53303230 *..OS/2 !! SYS020* +0000:7Dd0 32370d0a 00...... ........ ........ *27... * + +OS/2 loader file name. + +0000:7Dd0 ........ ..4f5332 424f4f54 20202020 * OS2BOOT * + +Data not used. + +0000:7De0 00000000 00000000 00000000 00000000 *................* +0000:7Df0 00000000 00000000 00000000 0000.... *.............. * + +The last two bytes contain a 55AAH signature. + +0000:7Df0 ........ ........ ........ ....55aa * U.* + +/end/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// diff --git a/etc/etc.i386/INSTALL.pt b/etc/etc.i386/INSTALL.pt new file mode 100644 index 00000000000..9cc21328dfe --- /dev/null +++ b/etc/etc.i386/INSTALL.pt @@ -0,0 +1,340 @@ + How it Works -- Partition Tables + + Version 1c + + by Hale Landis (landis@sugs.tware.com) + + +THE "HOW IT WORKS" SERIES + +This is one of several How It Works documents. The series +currently includes the following: + +* How It Works -- CHS Translation +* How It Works -- Master Boot Record +* How It Works -- DOS Floppy Boot Sector +* How It Works -- OS2 Boot Sector +* How It Works -- Partition Tables + + +PARTITION SECTOR/RECORD/TABLE BASICS + +FDISK creates all partition records (sectors). The primary +purpose of a partition record is to hold a partition table. The +rules for how FDISK works are unwritten but so far most FDISK +programs (DOS, OS/2, WinNT, etc) seem to follow the same basic +idea. + +First, all partition table records (sectors) have the same +format. This includes the partition table record at cylinder 0, +head 0, sector 1 -- what is known as the Master Boot Record +(MBR). The last 66 bytes of a partition table record contain a +partition table and a 2 byte signature. The first 446 bytes of +these sectors usually contain a program but only the program in +the MBR is ever executed (so extended partition table records +could contain something other than a program in the first 466 +bytes). See "How It Works -- The Master Boot Record". + +Second, extended partitions are "nested" inside one another and +extended partition table records form a "linked list". I will +attempt to show this in a diagram below. + +PARTITION TABLE ENTRY FORMAT + +Each partition table entry is 16 bytes and contains things like +the start and end location of a partition in CHS, the start in +LBA, the size in sectors, the partition "type" and the "active" +flag. Warning: older versions of FDISK may compute incorrect +LBA or size values. And note: When your computer boots itself, +only the CHS fields of the partition table entries are used +(another reason LBA doesn't solve the >528MB problem). The CHS +fields in the partition tables are in L-CHS format -- see "How It +Works -- CHS Translation". + +There is no central clearing house to assign the codes used in +the one byte "type" field. But codes are assigned (or used) to +define most every type of file system that anyone has ever +implemented on the x86 PC: 12-bit FAT, 16-bit FAT, HPFS, NTFS, +etc. Plus, an extended partition also has a unique type code. + +Note: I know of no complete list of all the type codes that have +been used to date. However, I try to include such a list in a +future version of this document. + +The 16 bytes of a partition table entry are used as follows: + + +--- Bit 7 is the active partition flag, bits 6-0 are zero. + | + | +--- Starting CHS in INT 13 call format. + | | + | | +--- Partition type byte. + | | | + | | | +--- Ending CHS in INT 13 call format. + | | | | + | | | | +-- Starting LBA. + | | | | | + | | | | | +-- Size in sectors. + | | | | | | + v <--+---> v <--+--> v v + + 0 1 2 3 4 5 6 7 8 9 A B C D E F + DH DL CH CL TB DL CH CL LBA..... SIZE.... + + 80 01 01 00 06 0e be 94 3e000000 0c610900 1st entry + + 00 00 81 95 05 0e fe 7d 4a610900 724e0300 2nd entry + + 00 00 00 00 00 00 00 00 00000000 00000000 3rd entry + + 00 00 00 00 00 00 00 00 00000000 00000000 4th entry + +Bytes 0-3 are used by the small program in the Master Boot Record +to read the first sector of an active partition into memory. The +DH, DL, CH and CL above show which x86 register is loaded when +the MBR program calls INT 13H AH=02H to read the active +partition's boot sector. See "How It Works -- Master Boot +Record". + +These entries define the following partitions: + +1) The first partition, a primary partition DOS FAT, starts at + CHS 0H,1H,1H (LBA 3EH) and ends at CHS 294H,EH,3EH with a size + of 9610CH sectors. + +2) The second partition, an extended partition, starts at CHS + 295H,0H,1H (LBA 9614AH) and ends at CHS 37DH,EH,3EH with a + size of 34E72H sectors. + +3) The third and fourth table entries are unused. + +PARTITION TABLE RULES + +Keep in mind that there are NO written rules and NO industry +standards on how FDISK should work but here are some basic rules +that seem to be followed by most versions of FDISK: + +1) In the MBR there can be 0-4 "primary" partitions, OR, 0-3 + primary partitions and 0-1 extended partition entry. + +2) In an extended partition there can be 0-1 "secondary" + partition entries and 0-1 extended partition entries. + +3) Only 1 primary partition in the MBR can be marked "active" at + any given time. + +4) In most versions of FDISK, the first sector of a partition + will be aligned such that it is at head 0, sector 1 of a + cylinder. This means that there may be unused sectors on the + track(s) prior to the first sector of a partition and that + there may be unused sectors following a partition table + sector. + + For example, most new versions of FDISK start the first + partition (primary or extended) at cylinder 0, head 1, sector + 1. This leaves the sectors at cylinder 0, head 0, sectors + 2...n as unused sectors. This same layout may be seen on the + first track of an extended partition. See example 2 below. + + Also note that software drivers like Ontrack's Disk Manager + depend on these unused sectors because these drivers will + "hide" their code there (in cylinder 0, head 0, sectors + 2...n). This is also a good place for boot sector virus + programs to hang out. + +5) The partition table entries (slots) can be used in any order. + Some versions of FDISK fill the table from the bottom up and + some versions of FDISK fill the table from the top down. + Deleting a partition can leave an unused entry (slot) in the + middle of a table. + +6) And then there is the "hack" that some newer OS's (OS/2 and + Linux) use in order to place a partition spanning or passed + cylinder 1024 on a system that does not have a CHS translating + BIOS. These systems create a partition table entry with the + partition's starting and ending CHS information set to all + FFH. The starting and ending LBA information is used to + describe the location of the partition. The LBA can be + converted back to a CHS -- most likely a CHS with more than + 1024 cylinders. Since such a CHS can't be used by the system + BIOS, these partitions can not be booted or accessed until the + OS's kernel and hard disk device drivers are loaded. It is + not known if the systems using this "hack" follow the same + rules for the creation of these type of partitions. + +There are NO written rules as to how an OS scans the partition +table entries so each OS can have a different method. For DOS, +this means that different versions could assign different drive +letters to the same FAT file system partitions. + +PARTITION NESTING + +What do I mean when I say the partitions are "nested" within each +other? Lets look at this example: + + M = Master Boot Record (and any unused sectors + on the same track) + E = Extended partition record (and any unused sectors + on the same track) + pri = a primary partition (first sector is a "boot" sector) + sec = a secondary partition (first sector is a "boot" sector) + + + |<----------------the entire disk-------------->| + | | + |M<pri> | + | | + | E<sec><---rest of 1st ext part---------->| + | | + | E<sec><---rest of 2nd ext part---->| + + +The first extended partition is described in the MBR and it +occupies the entire disk following the primary partition. The +second extended partition is described in the first extended +partition record and it occupies the entire disk following the +first secondary partition. + +PARTITION TABLE LINKING + +What do I mean when I say the partition records (tables) form a +"linked" list? This means that the MBR has an entry that +describes (points to) the first extended partition, the first +extended partition table has an entry that describes (points to) +the second extended partition table, and so on. There is, in +theory, no limited to out long this linked list is. When you ask +FDISK to show the DOS "logical drives" it scans the linked list +looking for all of the DOS FAT type partitions that may exist. +Remember that in an extended partition table, only two entries of +the four can be used (rule 2 above). + +And one more thing... Within a partition, the layout of the file +system data varies greatly. However, the first sector of a +partition is expected to be a "boot" sector. A DOS FAT file +system has: a boot sector, first FAT sectors, second FAT +sectors, root directory sectors and finally the file data area. +See "How It Works -- OS2 Boot Sector". + + +EXAMPLE 1 + +A disk containing four DOS FAT partitions (C, D, E and F): + + + |<---------------------the entire disk------------------->| + | | + |M<---C:---> | + | | + | E<---D:---><-rest of 1st ext part------------>| + | | + | E<---E:---><-rest of 2nd ext part->| + | | + | E<---------F:---------->| + + +EXAMPLE 2 + +So here is an example of a disk with two primary partitions, one +DOS FAT and one OS/2 HPFS, plus an extended partition with +another DOS FAT: + + + |<------------------the entire disk------------------>| + | | + |M<pri 1 - DOS FAT> | + | | + | <pri 2 - OS/2 HPFS> | + | | + | E<sec - DOS FAT>| + + +Or in more detail ('n' is the highest cylinder, head or sector +number number allowed in the indicated field of the CHS)... + + + +-------------------------------------+ + CHS=0,0,1 | Master Boot Record containing | + | partition table search program and | + | a partition table | + | +---------------------------------+ | + | | DOS FAT partition description | | points to CHS=0,1,1 + | +---------------------------------+ | points to CHS=a + | | OS/2 HPFS partition description | | + | +---------------------------------+ | + | | unused table entry | | + | +---------------------------------+ | + | | extended partition entry | | points to CHS=b + | +---------------------------------+ | + +-------------------------------------+ +CHS=0,0,2 | the rest of "track 0" -- this is | : +to | where the software drivers such as | : normally +CHS=0,0,n | Ontrack's Disk Manager or Micro | : unused + | House's EZ Drive are located. | : + +-------------------------------------+ +CHS=0,1,1 | Boot sector for the DOS FAT | : + | partition | : a DOS FAT + +-------------------------------------+ : file +CHS=0,1,2 | rest of the DOS FAT partition | : system +to | (FAT table, root directory and | : +CHS=x-1,n,n | user data area) | : + +-------------------------------------+ +CHS=x,0,1 | Boot sector for the OS/2 HPFS | : + | file system partition | : an OS/2 + +-------------------------------------+ : HPFS file +CHS=x,0,2 | rest of the OS/2 HPFS file system | : system +to | partition | : +CHS=y-1,n,n | | : + +-------------------------------------+ +CHS=y,0,1 | Partition record for the extended | + | partition containing a partition | + | record program (never executed) and | + | a partition table | + | +---------------------------------+ | + | | DOS FAT partition description | | points to CHS=b+1 + | +---------------------------------+ | + | | unused table entry | | + | +---------------------------------+ | + | | unused table entry | | + | +---------------------------------+ | + | | unused table entry | | + | +---------------------------------+ | + +-------------------------------------+ +CHS=y,0,2 | the rest of the first track of the | : normally +to | extended partition | : unused +CHS=y,0,n | | : + +-------------------------------------+ +CHS=y,1,1 | Boot sector for the DOS FAT | : + | partition | : a DOS FAT + +-------------------------------------+ : file +CHS=y,1,2 | rest of the DOS FAT partition | : system +to | (FAT table, root directory and | : +CHS=n,n,n | user data area) | : + +-------------------------------------+ + +EXAMPLE 3 + +Here is a partition record from an extended partition (the first +sector of an extended partition). Note that it contains no +program code. It contains only the partition table and the +signature data. + +OFFSET 0 1 2 3 4 5 6 7 8 9 A B C D E F *0123456789ABCDEF* +000000 00000000 00000000 00000000 00000000 *................* +000010 TO 0001af SAME AS ABOVE +0001b0 00000000 00000000 00000000 00000001 *................* +0001c0 8195060e fe7d3e00 0000344e 03000000 *.....}>...4N....* +0001d0 00000000 00000000 00000000 00000000 *................* +0001e0 00000000 00000000 00000000 00000000 *................* +0001f0 00000000 00000000 00000000 000055aa *..............U.* + +NOTES + +Thanks to yue@heron.Stanford.EDU (Kenneth C. Yue) for pointing +out that in V0 of this document I did not properly describe the +unused sectors normally found around the partition table sectors. + +/end/ +-- +\\===============\\=======================\\ + \\ Hale Landis \\ 303-548-0567 \\ + // Niwot, CO USA // landis@sugs.tware.com // +//===============//=======================// |