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Diffstat (limited to 'sys/arch/i386/boot/README.MACH')
| -rw-r--r-- | sys/arch/i386/boot/README.MACH | 207 |
1 files changed, 0 insertions, 207 deletions
diff --git a/sys/arch/i386/boot/README.MACH b/sys/arch/i386/boot/README.MACH deleted file mode 100644 index 8a895226364..00000000000 --- a/sys/arch/i386/boot/README.MACH +++ /dev/null @@ -1,207 +0,0 @@ -/* $NetBSD: README.MACH,v 1.5 1994/10/27 04:14:28 cgd Exp $ */ - -/* - * Ported to boot 386BSD by Julian Elischer, September 1992 - * - * Mach Operating System - * Copyright (c) 1992, 1991 Carnegie Mellon University - * All Rights Reserved. - * - * Permission to use, copy, modify and distribute this software and its - * documentation is hereby granted, provided that both the copyright - * notice and this permission notice appear in all copies of the - * software, derivative works or modified versions, and any portions - * thereof, and that both notices appear in supporting documentation. - * - * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" - * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR - * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. - * - * Carnegie Mellon requests users of this software to return to - * - * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU - * School of Computer Science - * Carnegie Mellon University - * Pittsburgh PA 15213-3890 - * - * any improvements or extensions that they make and grant Carnegie Mellon - * the rights to redistribute these changes. - */ - -********NOTE: This is not all relevant to the 386BSD version********** - - AT386 Protected Mode Bootstrap Loader - ===================================== - -1. Overview of Startup - ------------------- - - After the system is rebooted, the BIOS bootstrap routine reads Sector - 1, Track 0 into memory at location 0000:7C00H. If location 0000:7DFEH - (last two bytes of that sector) contains the value AA55H, the BIOS - bootstrap routine will transfer control to 0000:7C00H. Otherwise, the - boot code in that sector is bad and the boot routine stops. - - For DOS compatibility reason, one extra stage of boot is required if - the boot device is a hard disk. The first sector of the hard disk will - contain the MOS-DOS boot code and a boot record partition table. - When this sector is loaded into 0000:7C00H, it will relocate itself - to somewhere else and then load the first sector of the active - partition into 0000:7C00H. Both UNIX and DOS use the command "fdisk" - to install this first sector into the hard disk and to manipulate - the hard disk partitions. - - - -2. The First Stage Bootstrap Loader - -------------------------------- - - After startup, the first stage boot is loaded at 0000:7C00H. This - first stage boot will load itself and the second stage boot into - memory at location 0000:1000H. For floppy disks, the first cylinder - is reserved as the boot cylinder, and the boot code (first and second) - will be loaded from there. Currently, only double sided, high density - (15 sectors per track) floppies are supported. For hard disks, the - first 29 sectors of the active partition is reserved for boot code - which will be loaded by the first stage boot. All the disk types - recognized by BIOS are supported by this bootstrap loader. - - - -3. The Second Stage Bootstrap Loader - -------------------------------- - - After the boot code is loaded, the control is passed to the second - stage bootstrap loader "boot2()". In order to be able to load the - big kernel image (bigger than 512K or 640K, depends on the memory - configuration), the second stage boot loader will run on the protected - mode. This bootstarp loader does not have any stand alone device - drivers, all the I/O's are through the BIOS calls. Since the first - stage boot code will no longer be used at this moment, the memory - location of the first stage boot code (0000:1000H to 0000:1200H) will - be used as an internal buffer for BIOS calls. Immediately after this -[For NetBSD, we have a different buffer which can hold an entire floppy -track.] - internal buffer is the GDT table for the second stage boot loader. - Since this boot loader needs to switch back and forth between protected - and real mode in order to use BIOS calls, the limit of the boot code - and boot data segments must not be greater than 64K. - - The boot loader loads the kernel image at memory location above 1 MB - to skip the memory hole between 521K/640K and 1MB. After the kernel - is loaded, the boot loader stores the information in the stack and - then passes control to kernel. Currently, the three information passed - fromm the boot loader to the kernel are type of the boot device, size - of the base memory and size of the extended memory. - -[NetBSD receives: howto, bootdev, esym.] - -[NetBSD is loaded where-ever the "MByte" bits of the load address specify; -normally the load address is F8100000, so it loads at 1MB.] - - -4. The UNIX Startup - ---------------- - - Since the boot loader loads the kernel image at memory location above - 1MB, the kernel has to start as protected mode. In addition, the - link editor description file (vuifile) has to indicate that - the text and data segments start above 1MB. Also, the boot loader - passes the infomation to the kernel through the stack. - -[MOST of what is mentionned below is NOT relevant to NetBSD.] - -5. Disk Layout and Bad Block Handling - --------------------------------- - - The System V/386 Release 3.2 (AT) disk layout will be used as the disk - layout for the MACH System on the AT platform. - - This disk layout is as follows: - - * Reserve the first sector of cylinder 0 for the DOS boot record which - contains the master boot code (446 bytes) and the partition table. - (Refer to DOS Technical Reference Manual page 9-6 to 9-10). - - * Reserve the first 29 sectors of the UNIX partition for the first - and the second stage bootstrap. - - * Reserve the 30th sector of the UNIX partition for the pdinfo and - the vtoc tables. - - * Reserve the 31st to the 34th sectors of the UNIX partition for the - bad track and the bad block mapping tables. - - * Reserve up to 253 consecutive tracks when required, beginning with - the 35th sector of the UNIX partition, for alternate tracks. - - * Reserve up to 253 consecutive blocks, beginning with the first - sector after the alternate tracks area, for alternate blocks. - - SEC - 1 - ---------------------------------------------------- - | X | | CYL 0, TRK 0 - ---------------- .......... -------------------- - | .......... | - ---------------- .......... -------------------- - | .......... | - =============================================================== - ^ | BOOTSTRAP | CYL N, TRK M - | ---------------------------------------------------- - | | |30 |31 |32 |33 |34 | - ---------------------------------------------------- --- - U | .......... | ^ - N ---------------- .......... --------------------- | - I | .......... | Alternate Tracks - X ---------------- .......... --------------------- | - | .......... | V - P ---------------------------------------------------- --- - A | .......... | ^ - R ---------------- .......... --------------------- | - T | .......... | Alternate Blocks - I ---------------- .......... -------------------- | - T | .......... | V - I ---------------------------------------------------- --- - O | Unix root partition starts from here | - N ---------------- ----------------- - | | - ---------------------------------------------------- - | | - ---------------------------------------------------- - | | - | --------------------------------------------------- - | | | - | ---------------------------------------------------- - V | | - =============================================================== - | ........ | - --------------- ........ -------------- - | ........ | - ---------------------------------------------------- - - - The bad block handling mechanism is as follows: - - * Use the alternate track in the alternate tracks area if the - track containing the target sector is bad. - - * Use the alternate block in the alternate blocks area if the - target sector is bad. - - - - -6. How to make: - ----------- - - Since the kernel image is loaded above 1 MB, the kernel must start - as protected mode. This means that this bootstrap loader will work - only when the corresponding changes on the kernel startup code are done. - - The make command to generate this bootstrap loader is: - - make -f boot.mk fdboot (floppy boot loader) - make -f boot.mk hdboot (wini boot loader) -[To make NetBSD bootblocks "make install" (warning: they will be installed -in /usr/mdec.. make backups).] |