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+<!DOCTYPE linuxdoc PUBLIC "-//Xorg//DTD linuxdoc//EN"[
+<!ENTITY % defs SYSTEM "defs.ent"> %defs;
+]>
+
+<article>
+
+<!-- Title information -->
+
+<title>ATI Adapters README file
+<author>Marc Aurele La France
+<date>2002 February 12
+
+
+
+
+
+<ident>
+$Id: README.ati.sgml,v 1.1 2006/11/26 20:00:37 matthieu Exp $ 
+Based on XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/ati.sgml,v 3.42 2003/01/20 03:43:07 dawes Exp 
+</ident>
+
+<abstract>
+This is the README for the XAA ATI driver included in this release.
+</abstract>
+
+<!-- Table of contents -->
+<toc>
+
+<!-- Begin the document -->
+
+<sect>Statement of intent<p>
+Generally speaking, the driver is intended for all ATI video adapters
+based on the Mach64 series or older chipsets,
+providing maximum video function within hardware limitations.
+The driver is also intended to optionally provide the same level of support for
+generic VGA or 8514/A adapters.
+The newer Rage 128 and Radeon chips are not yet supported by this driver.
+Rage 128's and Radeon's are, however, supported by separate drivers, and
+owners of such adapters should consult the documentation provided with these
+drivers.
+This driver will also invoke the appropriate driver if it finds Rage 128 and/or
+Radeon adapter(s) in the system.
+This driver is still being actively developed, meaning that it currently does
+not yet fully meet these goals.<p>
+The driver will provide
+<itemize>
+<item>accelerated support if an ATI accelerator is detected <it>and</it> the
+user has not requested that this support be disabled;  otherwise
+<item>accelerated support if a non-ATI 8514/A-capable adapter is detected
+<it>and</it> the user has requested such support;  otherwise
+<item>unaccelerated SuperVGA support if an ATI VGA-capable adapter is detected;
+otherwise
+<item>generic VGA support if a non-ATI VGA-capable adapter is detected
+<it>and</it> the user has requested such support.
+</itemize>
+Thus, the level of support provided not only depends on what the driver detects
+in the system, but also, on what the user specifies in the xorg.conf file.
+See the <bf>``xorg.conf specifications''</bf> section below for details.<p>
+If none of the above conditions are met, the ATI driver will essentially
+disable itself to allow other drivers to examine the system.<p>
+<!-- 
+Note that I am currently considering removing the driver's support for generic
+VGA.
+If you have any concerns about this, please contact me at
+<email>tsi@xfree86.org</email>.
+-->
+<sect>A note on acceleration<p>
+The meaning of ``acceleration'', as used in this document, needs to be
+clarified.
+Two of the many components in an accelerator are the CRT controller (CRTC) and
+the Draw Engine.
+This is in addition to another CRTC that, generally, is also present in the
+system (often in the same chip) and typically provides EGA, VGA or SuperVGA
+functionality.<p>
+A CRTC is the component of a graphics controller that is responsible for
+reading video memory for output to the screen.
+A Draw Engine is an accelerator component that can be programmed to manipulate
+video memory contents, thus freeing the CPU for other tasks.<p>
+When the VGA CRTC is used, all drawing operations into video memory are the
+responsibility of the system's CPU, i.e. no Draw Engine can be used.
+On the other hand, if the accelerator's CRTC is chosen to drive the screen,
+the Draw Engine can also be used for drawing operations, although the CPU can
+still be used for this purpose if it can access the accelerator's video
+memory.<p>
+Video acceleration refers to the programming of an accelerator's Draw Engine to
+offload drawing operations from the CPU, and thus also implies the use of the
+accelerator's CRTC.<p>
+<sect>Current implementation for ATI adapters<p>
+The driver currently supports the SuperVGA capabilities of all ATI adapters
+except some early Mach8 and Mach32 adapters that do not provide the required
+functionality.
+This support works for monochrome, 16-colour and 256-colour video modes, if one
+of the following ATI graphics controller chips is present:
+<verb>
+VGAWonder series:  18800, 18800-1, 28800-2, 28800-4, 28800-5, 28800-6
+   Mach32 series:  68800-3, 68800-6, 68800AX, 68800LX
+   Mach64 series:  88800GX-C, 88800GX-D, 88800GX-E, 88800GX-F, 88800CX,
+                   264CT, 264ET, 264VT, 264GT (3D Rage), 264VT-B, 264VT3,
+                   264VT4, 264GT-B (3D Rage II), 3D Rage IIc, 3D Rage Pro,
+                   3D Rage LT, 3D Rage LT Pro, 3D Rage XL, 3D Rage XC,
+                   3D Rage Mobility (including the -M and -P variants)</verb>
+The driver also supports 32K, 64K and 16M-colour modes on the 264xT and 3D Rage
+series of adapters using the accelerator CRTC (but not the VGA CRTC).<p>
+The newer Rage 128 and Radeon chips are not yet supported by this driver.
+Rage 128's and Radeon's are, however, supported by separate drivers, and
+owners of such adapters should consult the documentation provided with these
+drivers.
+This driver will also invoke the appropriate driver if it finds Rage 128 and/or
+Radeon adapter(s) in the system.<p>
+Adapters based on the above chips have been marketed under a rather large
+number of names over the years.
+Among them are:
+<verb>
+VGAWonder series:  VGAWonder V3, VGAWonder V4, VGAWonder V5, VGAWonder+,
+                   VGAWonder XL, VGAWonder XL24, VGAWonder VLB, VGA Basic,
+                   VGA Basic 16, VGA Edge, VGA Edge 16, VGA Integra,
+                   VGA Charger, VGAStereo F/X, VGA 640, VGA 800, VGA 1024,
+                   VGA 1024D, VGA 1024 XL, VGA 1024 DXL, VGA 1024 VLB
+    Mach8 series:  Graphics Ultra, Graphics Vantage, VGAWonder GT
+                   (None of the 8514/Ultra and 8514 Vantage series is
+                    supported at this time)
+   Mach32 series:  Graphics Ultra+, Graphics Ultra Pro, Graphics Wonder,
+                   Graphics Ultra XLR, Graphics Ultra AXO, VLB mach32-D,
+                   PCI mach32-D, ISA mach32
+   Mach64 series:  Graphics Xpression, Graphics Pro Turbo, WinBoost,
+                   WinTurbo, Graphics Pro Turbo 1600, Video Xpression,
+                   3D Xpression, Video Xpression+, 3D Xpression+,
+                   3D Charger, Video Charger, WinCharger, All-In-Wonder,
+                   All-In-Wonder PRO, 3D Pro Turbo, XPERT@Play,
+                   XPERT@Play 98, XPERT@Work, XPERT 98, XPERT LCD,
+                   XPERT XL</verb>
+Also, a number of mainboards, laptops and notebooks harbour a Mach32 or Mach64
+controller.<p>
+VGAWonder, Mach8 and Mach32 ISA adapters are available with or without a
+mouse.<p>
+These adapters are available with a variety of clock generators and RAMDACs.
+The 264xT and 3D Rage series of chips are integrated controllers, meaning that
+they include a programmable clock generator and a RAMDAC.<p>
+For all but Mach64 adapters, this driver still does not provide support for
+accelerated drawing to the screen.
+This means that all drawing is done by the CPU, rather than by any accelerator
+present in the system.
+This can make opaque moves, for example, quite ``jerky''.
+Also, given that IBM 8514/A and ATI Mach8 do not allow CPU access to their
+frame buffer, the driver will currently ignore these accelerators.
+Most Mach32 adapters provide both accelerated function and SuperVGA
+functionality, but the driver currently only uses the VGA.<p>
+The driver <it>does</it> however support the accelerator CRTC present in all
+ATI Mach64 adapters.
+For 256-colour, and higher depth modes, this support will be used by default,
+although an xorg.conf option can be specified to use the SuperVGA CRTC
+instead.
+A linear video memory aperture is also available in 256-colour and higher depth
+modes and enabled by default if a 264xT or 3D Rage controller is detected or,
+on 88800 controllers, if the accelerator CRTC is used.
+xorg.conf options are available to disable this aperture, or (for non-PCI
+adapters) enable it or move it to some other address.<p>
+By default, the driver provides some acceleration for Mach64 if the accelerator
+CRTC is used, and modes whose colour depth greater than or equal to 8 are to be
+used.
+This support is as yet incomplete and can be disabled entirely with an
+xorg.conf option.<p>
+On non-Intel platforms, the driver can, currently, only support PCI Mach64
+adapters.<p>
+<sect>Current implementation of generic VGA support for non-ATI adapters<p>
+Support for generic VGA with non-ATI adapters is also implemented, but has
+undergone only limited testing.
+The driver will intentionally disallow the use of this support with ATI
+adapters.
+This support must be explicitly requested through an xorg.conf ChipSet
+specification.
+This prevents the current VGA generic driver from being disabled.<p>
+This driver's generic VGA support is intended as an extension of that provided
+by the current generic driver.
+Specifically, within the architectural bounds defined by IBM's VGA standard,
+this driver will allow the use of any 256-colour mode, and any dot clock
+frequencies both of which allow for many more mode possibilities.<p>
+The driver will enforce the following limitations derived from IBM's original
+VGA implementation:
+<itemize>
+<item>There can only be a set of four (non-programmable) clocks to choose from.
+<item>Video memory is limited to 256kB in monochrome and 16-colour modes.
+<item>Video memory is limited to 64kB in 256-colour modes.
+<item>Interlaced modes are not available.
+<item>Colour depths higher than 8 are not available.
+</itemize>
+<sect>xorg.conf specifications<p>
+The driver recognises a number of xorg.conf options.
+In general, all such options should be specified in a ``Device'' section, and
+affect only that ``Device'' section.<p>
+Those options that affect how the driver associates adapters with ``Device''
+sections are described first.
+The driver will ignore (with a message) a ``Device'' section if the section
+cannot be associated with exactly one adapter in the system.
+Similarly, the driver will ignore, or disable, (with a message) any adapter
+that cannot be associated with exactly one ``Device'' section.
+Thus, these options will be required in those uncommon cases where such unique
+associations cannot automatically be made by the driver.<p>
+Other options affect the driver's operation once an adapter has been assigned
+to the ``Device'' section which contains them.<p>
+<sect1>Driver ``ati''<p>
+The use of this specification is highly recommended if the ``Device'' section
+is to be recognised by the driver.
+In fact, it is almost (but not quite) mandatory, particularly when using the
+loader server as it indicates what driver is to be loaded and associated with
+the ``Device'' section.<p>
+<sect1>ChipSet ``name''<p>
+The default ChipSet name for this driver is ``<it>ati</it>''.
+In this case, any ATI adapter can be associated with the ``Device'' section.
+If an ATI accelerator is detected and the driver supports it, the accelerator's
+CRTC will be used to drive the screen.
+Otherwise, the driver will programme the adapter's SuperVGA CRTC.<p>
+If ``<it>ativga</it>'' is specified instead, the driver will ignore any ATI
+accelerator it detects, but otherwise operate as if ``<it>ati</it>'' had been
+specified.
+This specification ensures the VGA CRTC is used.<p>
+A ChipSet name of ``<it>ibmvga</it>'' causes any VGA-capable adapter in the
+system to be associated with the ``Device'' section.
+It enables the driver's generic VGA support, but only for non-ATI adapters.
+If an ATI adapter is associated with the ``Device'' section, the driver will
+operate as if ``<it>ativga</it>'' had been specified instead.<p>
+A ChipSet name of ``<it>vgawonder</it>'' is equivalent to ``<it>ativga</it>'',
+except that only VGAWonder-capable adapters can be assigned to the ``Device''
+section.
+This specifically excludes the newer integrated Mach64 controllers.<p>
+In some PCI or AGP systems, the driver will not, by default, probe for non-PCI
+Mach32's or Mach64's.
+This is because, before doing any such probe, the driver attempts to determine
+if the probe can cause a lockup.
+If the driver has enough information to determine that a lockup would occur, it
+will skip the probe.
+In some situations, this determination cannot be accurate, and the driver will
+err on the side of caution, skipping the probe.
+Specifying a ChipSet name of ``<it>mach32</it>'' or ``<it>mach64</it>'', as
+appropriate, will force the driver to probe for the non-PCI adapter.
+These ChipSet names should, therefore, only be used when there is in fact such
+an adapter in the system.
+They are otherwise equivalent to ``<it>ati</it>''.<p>
+On non-Intel platforms, only ``<it>ati</it>'' and ``<it>mach64</it>'' ChipSet
+values are operative.<p>
+<sect1>ChipID & ChipRev specifications<p>
+These specifications will cause the driver to associate the ``Device'' section
+only with an adapter having the same attributes, or an adapter whose PCI device
+ID the driver does not recognise.
+In the second case, these options cause the driver to treat the adapter as if
+it was one with the specified PCI device ID or revision.
+ChipID can only be used with Mach32 or Mach64 adapters, and, thus, specifically
+excludes any other adapter from matching the ``Device'' section.
+ChipRev is meaningful only with Mach64 adapters, and then only if ChipID is
+also specified in the same ``Device'' section.<p>
+<sect1>IOBase<p>
+This option limits the adapters that can be associated with the ``Device''
+section to the one with the specified I/O base.
+This option only applies to Mach64 adapters and specifically excludes other
+adapters.<p>
+<sect1>BusID<p>
+This option limits the adapters that can be associated with the ``Device''
+section to the one with the specified PCI Bus ID.
+This specification excludes non-PCI adapters.<p>
+<sect1>Clocks<p>
+For the purpose of specifying a clock line in your xorg.conf, one of four
+different situations can occur, as follows.<p>
+Those configuring the driver's generic VGA support for a non-ATI adapter,
+can skip ahead to the <bf>``Clocks for non-ATI adapters''</bf> section below.
+Those <it>not</it> trying to configure the driver for a Mach64 adapter, can
+skip ahead to the <bf>``Clocks for fixed clock generators on ATI
+adapters''</bf> section below.<p>
+The very earliest Mach64 adapters use fixed (i.e. non-programmable) clock
+generators.
+Very few of these (mostly prototypes) are known to exist, but if you have one
+of these, you can also skip ahead to the <bf>``Clocks for fixed clock
+generators on ATI adapters''</bf> section below.<p>
+The two cases that are left deal with programmable clock generators, which are
+used on the great majority of Mach64 adapters.<p>
+If you are uncertain which situation applies to your adapter, you can run a
+clock probe with the command ``<tt>X -probeonly</tt>''.<p>
+<sect2>Clocks for supported programmable clock generators<p>
+At bootup, video BIOS initialisation programmes an initial set of frequencies.
+Two of these are reserved to allow the setting of modes that do not use a
+frequency from this initial set.
+One of these reserved slots is used by the BIOS mode set routine, the other by
+the particular driver used (e.g. MS-Windows, AutoCAD, X, etc.).
+The clock numbers reserved in this way are dependent on the particular clock
+generator used by the adapter.<p>
+The driver currently supports all programmable clock generators known to exist
+on Mach64 adapters.
+In this case, the driver will completely ignore any xorg.conf clock
+specification, and programme the clock generator as needed by the modes used
+during the X session.<p>
+<sect2>Clocks for unsupported programmable clock generators<p>
+This case is unlikely to occur, but is documented for the sake of
+completeness.<p>
+In this situation, the driver will probe the adapter for clock frequencies
+unless xorg.conf clocks are already specified.
+In either case, the driver will then attempt to normalise the clocks to one of
+the following specifications:
+<verb>
+BIOS setting 1:
+
+  Clocks   0.000 110.000 126.000 135.000  50.350  56.640  63.000  72.000
+           0.000  80.000  75.000  65.000  40.000  44.900  49.500  50.000
+           0.000  55.000  63.000  67.500  25.180  28.320  31.500  36.000
+           0.000  40.000  37.500  32.500  20.000  22.450  24.750  25.000</verb>
+<verb>
+BIOS setting 2:
+
+  Clocks   0.000 110.000 126.000 135.000  25.180  28.320  31.500  36.000
+           0.000  80.000  75.000  65.000  40.000  44.900  49.500  50.000
+           0.000  55.000  63.000  67.500  12.590  14.160  15.750  18.000
+           0.000  40.000  37.500  32.500  20.000  22.450  24.750  25.000</verb>
+<verb>
+BIOS setting 3:
+
+  Clocks   0.000   0.000   0.000   0.000  25.180  28.320   0.000   0.000
+           0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000
+           0.000   0.000   0.000   0.000  12.590  14.160   0.000   0.000
+           0.000   0.000   0.000   0.000   0.000   0.000   0.000   0.000</verb>
+If the driver matches the clocks to the third setting above, functionality will
+be <it>extremely</it> limited (assuming the driver works at all).<p>
+<sect2>Clocks for fixed clock generators on ATI adapters<p>
+This section applies to all VGAWonder and Mach32 adapters, and to early Mach64
+prototypes.<p>
+One of the following clocks specifications (or an initial subset thereof) can
+be used depending on what the adapter uses to generate dot clocks:
+<verb>
+Crystals (VGA Wonder V3 and V4 adapters only):
+
+  Clocks  50.000  56.644   0.000  44.900  44.900  50.000   0.000  36.000
+          25.000  28.322   0.000  22.450  22.450  25.000   0.000  18.000
+          16.667  18.881   0.000  14.967  14.967  16.667   0.000  12.000
+          12.500  14.161   0.000  11.225  11.225  12.500   0.000   9.000</verb>
+<verb>
+ATI 18810 clock generator:
+
+  Clocks  30.240  32.000  37.500  39.000  42.954  48.771   0.000  36.000
+          40.000   0.000  75.000  65.000  50.350  56.640   0.000  44.900
+          15.120  16.000  18.750  19.500  21.477  24.386   0.000  18.000
+          20.000   0.000  37.500  32.500  25.175  28.320   0.000  22.450
+          10.080  10.667  12.500  13.000  14.318  16.257   0.000  12.000
+          13.333   0.000  25.000  21.667  16.783  18.880   0.000  14.967
+           7.560   8.000   9.375   9.750  10.739  12.193   0.000   9.000
+          10.000   0.000  18.750  16.250  12.586  14.160   0.000  11.225</verb>
+<verb>
+ATI 18811-0 and ATI 18812-0 clock generators:
+
+  Clocks  30.240  32.000 110.000  80.000  42.954  48.771  92.400  36.000
+          39.910  44.900  75.000  65.000  50.350  56.640   0.000  44.900
+          15.120  16.000  55.000  40.000  21.477  24.386  46.200  18.000
+          19.955  22.450  37.500  32.500  25.175  28.320   0.000  22.450
+          10.080  10.667  36.667  26.667  14.318  16.257  30.800  12.000
+          13.303  14.967  25.000  21.667  16.783  18.880   0.000  14.967
+           7.560   8.000  27.500  20.000  10.739  12.193  23.100   9.000
+           9.978  11.225  18.750  16.250  12.588  14.160   0.000  11.225</verb>
+<verb>
+ATI 18811-1 and ATI 18811-2 clock generators:
+
+  Clocks 135.000  32.000 110.000  80.000 100.000 126.000  92.400  36.000
+          39.910  44.900  75.000  65.000  50.350  56.640   0.000  44.900
+          67.500  16.000  55.000  40.000  50.000  63.000  46.200  18.000
+          19.955  22.450  37.500  32.500  25.175  28.320   0.000  22.450
+          45.000  10.667  36.667  26.667  33.333  42.000  30.800  12.000
+          13.303  14.967  25.000  21.667  16.783  18.880   0.000  14.967
+          33.750   8.000  27.500  20.000  25.000  31.500  23.100   9.000
+           9.978  11.225  18.750  16.250  12.588  14.160   0.000  11.225</verb>
+<verb>
+ICS 2494-AM clock generators (found on some Dell motherboards):
+
+  Clocks  75.000  77.500  80.000  90.000  25.175  28.322  31.500  36.000
+         100.000 110.000 126.000 135.000  40.000  44.900  50.000  65.000
+          37.500  38.750  40.000  45.000  12.588  14.161  15.750  18.000
+          50.000  55.000  63.000  67.500  20.000  22.450  25.000  32.500
+          25.000  25.833  26.667  30.000   8.392   9.441  10.500  12.000
+          33.333  36.667  42.000  45.000  13.333  14.767  16.667  21.667
+          18.750  19.375  20.000  22.500   6.294   7.081   7.875   9.000
+          25.000  27.500  31.500  33.750  10.000  11.225  12.500  16.250</verb>
+VGAWonder VLB, VGA 1024 VLB, Mach32 and Mach64 owners should only specify up to
+the first 32 frequencies.
+Any more will be ignored.<p>
+Other clock generators that have been used on ATI adapters (which can all be
+said to be clones of one of the above) might generate non-zero frequencies for
+those that are zero above, or vice-versa.<p>
+The order of the clocks <it>is</it> very important, although the driver will
+reorder the specified clocks if it deems it appropriate to do so.
+Mach32 and Mach64 owners should note that this order is different than what
+they would use for previous accelerated servers.<p>
+<sect2>Clocks for non-ATI adapters<p>
+If no clocks are specified in the xorg.conf, the driver will probe for four
+clocks, the second of which will be assumed to be 28.322 MHz.
+The first clock will typically be 25.175 MHz, but there are exceptions.
+You can include up to four clock frequencies in your xorg.conf to specify the
+actual values used by the adapter.
+Any more will be ignored.<p>
+<sect1>Option <it>``nopanel_display''</it><p>
+This specification is only effective when the driver detects that the adapter's
+BIOS has initialised both the digital flat panel and CRT interfaces.
+In such a situation, the driver will normally drive both the panel and the CRT.
+This specification causes the driver to disable the digital flat panel and
+display the screen image on the CRT instead, which could potentially allow for
+larger physical resolutions than the panel can handle.<p>
+<sect1>Option <it>``crt_display''</it><p>
+This specification is only effective when the driver detects that the adapter's
+BIOS has initialised the digital flat panel interface, but has disabled the
+CRT interface.
+In such a situation the driver will normally drive only the panel.
+This specification causes the driver to instead display the same image on both
+the panel and the CRT.<p>
+<sect1>Option <it>``noaccel''</it><p>
+By default, the driver will accelerate draw operations if a Mach64 CRTC is used
+to drive the display.
+As implemented in this driver, acceleration does not require a linear video
+memory aperture.
+This option disables this acceleration.<p>
+<sect1>Option <it>``nolinear''</it><p>
+By default, the driver will enable a linear video memory aperture for
+256-colour and higher depth modes if it is also using a Mach64 accelerator CRTC
+or an integrated Mach64 graphics chip.
+This option disables this linear aperture.<p>
+On non-Intel platforms, the driver requires a linear aperture and, so, this
+option is ignored.<p>
+<sect1>Option <it>``HWCursor''</it> and Option <it>``SWCursor''</it><p>
+Option <it>``HWCursor''</it>, which is the default, specifies that hardware
+facilities are to be used to paint the mouse pointer on the screen.
+Option <it>``SWCursor''</it> specifies that the mouse pointer is to be drawn by
+software, which is much slower.
+If both options are specified, option <it>``SWCursor''</it> prevails.
+Currently, these options are only acted upon for 256-colour or higher depth
+modes, if a Mach64 accelerator CRTC, or a Mach64 integrated controller is being
+used.
+In all other situations, a software cursor will be used, regardless of what
+these options specify.<p>
+<sect1>Option <it>``SilkenMouse''</it><p>
+This option is only acted upon when a hardware cursor is being used.
+It specifies that the cursor's position on the screen is to be updated as
+quickly as possible when the mouse is moved.
+This is the default behaviour.
+If this option is negated, the cursor may lag the mouse when the X server is
+very busy.<p>
+<sect1>Option <it>``shadowfb''</it><p>
+If this option is enabled, the driver will cause the CPU to do each drawing
+operation first into a shadow frame buffer in system virtual memory and then
+copy the result into video memory.
+If this option is not active, the CPU will draw directly into video memory.
+Enabling this option is beneficial for those systems where reading from video
+memory is, on average, slower than the corresponding read/modify/write
+operation in system virtual memory.
+This is normally the case for PCI or AGP adapters, and, so, this option is
+enabled by default.
+For other bus types, the default behaviour is to disable this option.<p>
+Note that, due to various limitations, this option is forcibly disabled when a
+linear video memory aperture is not enabled, when the frame buffer depth is
+less than 8, or when acceleration is used.<p>
+<sect1>Option <it>``dpms''</it><p>
+This option enables the driver's support for VESA's Display Power Management
+Specification.<p>
+<sect1>Option <it>``backingstore''</it><p>
+This is not specifically a driver option.
+It is used to enable the server's support for backing store, a mechanism by
+which pixel data for occluded window regions is remembered by the server
+thereby alleviating the need to send expose events to X clients when the data
+needs to be redisplayed.<p>
+<sect1>MemBase <it>address</it><p>
+This specification is only effective for non-PCI Mach64 adapters, and is used
+to override the CPU address at which the adapter will map its video memory.
+Normally, for non-PCI adapters, this address is set by a DOS install utility
+provided with the adapter.
+The MemBase option can also be used to enable the linear aperture in those
+cases where ATI's utility was not, or can not be, used.<p>
+For PCI and AGP adapters, this address is determined at system bootup according
+to the PCI Plug'n'Play specification which arbitrates the resource requirements
+of most devices in the system.
+This means the driver can not easily change the linear aperture address.<p>
+<sect1>Option <it>``ReferenceClock''</it> ``frequency''<p>
+This option is only applicable to non-Intel platforms, where an adapter BIOS is
+not available to the driver.
+The option specifies the reference frequency used by the adapter's clock
+generator.
+The default is 14.318 MHz, and other typical values are 28.636, or 29.5 MHz.<p>
+<sect1>ClockChip <it>``name''</it><p>
+This option is only applicable to non-Intel platforms, where an adapter BIOS is
+not available to the driver, and the driver cannot reliably determine whether
+the clock generator the adapter uses is a variant of an ATI 18818 (a.k.a.
+ICS 2595) or an unsupported clock generator.
+The only values that are acted upon are <it>``ATI 18818-0''</it> or
+<it>``ATI 18818-1''</it>.
+From this specification, the driver derives a reference divider of 43 or 46
+(respectively) for use in clock programming calculations.
+The driver's default behaviour, in this case, is to assume an unsupported clock
+generator, which means it will treat it as a fixed-frequency clock generator,
+as described under the heading <bf>``Clocks for unsupported programmable clock
+generators''</bf> above.<p>
+<sect>Video modes<p>
+Mode timings can be derived from the information in X's doc subdirectory.
+However, it is no longer required to specify such timings in an xorg.conf's
+``Monitor'' section(s), if only standard mode timings are to be used.
+The server automatically inserts VESA standard mode timings in every
+``Monitor'' section, and these modes will be checked first for mode constraints
+(monitor sync tolerances, video memory size, etc.).<p>
+Furthermore, it is also no longer required to specify mode names in ``Display''
+subsections.
+Should no mode names be specified (or those specified do not yield a usable
+mode), the server will automatically select as a default resolution the largest
+usable mode, whether or not the chosen mode is specified in the corresponding
+``Monitor'' section.<p>
+For a digital flat panel, any sync tolerances should be removed from the
+corresponding ``Monitor'' section.
+The driver will automatically calculate these from the mode that is active on
+server entry.
+The driver also inserts timings for a mode called <it>"Native panel mode"</it>
+that represents the panel's native resolution.<p>
+<sect>Known problems and limitations<p>
+There are several known problems or limitations related to the ATI
+driver.
+They include:<p>
+<itemize>
+<item>When using a Mach64's accelerator CRTC, the virtual resolution must be
+less than 8192 pixels wide.
+The VGA CRTC further limits the virtual resolution width to less than 4096
+pixels, or to less than 2048 pixels for adapters based on 18800-x's (with 256kB
+of memory) and on Mach64 integrated controllers.
+These are hardware limits that cannot be circumvented.
+<item>Virtual resolutions requiring more than 1MB of video memory (256kB in the
+monochrome case) are not supported by the VGA CRTC on 88800GX and 88800CX
+adapters.
+This is a hardware limit that cannot be circumvented.
+<item>Due to hardware limitations, doublescanned modes are not supported by the
+accelerator CRTC in 88800GX, 88800CX, 264CT and 264ET adapters.
+<item>The ``VScan'' modeline parameter is only supported when using the VGA
+CRTC.
+<item>Interlaced modes are not supported on 18800-x and 28800-x adapters when
+using a virtual resolution that is 2048 pixels or wider.
+When using a 18800-x with 256kB of video memory in 256-colour modes, this limit
+is reduced to 1024.
+This is yet another hardware limitation that cannot be circumvented.
+<item>Video memory banking does not work in monochrome and 16-colour modes on
+18800-x adapters.
+This appears to be another hardware limit, but this conclusion cannot be
+confirmed at this time.
+The driver's default behaviour in this case is to limit video memory to 256kB.
+<item>Video memory corruption can still occur during mode switches on 18800-x
+adapters.
+Symptoms of this problem include garbled fonts on return to text mode, and
+various effects (snow, dashed lines, etc) on initial entry into a graphics
+mode.
+In the first case, the workaround is to use some other means of restoring the
+text font.
+On Linux, this can be accomplished with the kbd or svgalib packages.
+In the second case, <htmlurl name="xrefresh(1)" url="xrefresh.1.html">
+will usually clean up the image.
+No complete solution to this problem is currently known.
+It appears this corruption occurs due to either video memory bandwidth or
+RAMDAC limitations, and so the driver will limit mode clocks to 40MHz.
+<item>There is some controversy over what the maximum allowed clock frequency
+should be on 264xT and 3D Rage adapters.
+For now, clocks will, by default, be limited to 80MHz, 135MHz, 170MHz, 200MHz
+or 230MHz, depending on the specific controller.
+This limit can only be increased (up to a driver-calculated absolute maximum)
+through the DACSpeed specification in xorg.conf.
+Be aware however that doing so is untested and might damage the adapter.
+<item>Except as in the previous items, clocks are limited to 80MHz on most
+adapters, although many are capable of higher frequencies.
+This will eventually be fixed in a future release.
+<item>The use of a laptop's hot-keys to switch displays while this driver is
+active can cause lockups and/or other woes, and is therefore not recommended.
+It is not currently possible to solve this problem.<p>
+<item>In situations where the driver is to simultaneously display on both a
+panel and a CRT, the same image will be seen on both.
+In particular, this means the CRT must be able to synchronise with the timings
+of the panel's native resolution.
+This is quite evident when the panel has ``odd-ball'' dimensions, such as
+1400x1050, a resolution not commonly possible on CRTs or projection
+equipment.<p>
+Also, the display of independent images on the panel and CRT is not currently
+implemented, and might never be, pending resolution of the previous item.<p>
+</itemize>
+Support for the following will be added in a future release:
+<itemize>
+<item>Mach32's accelerator CRTC.
+This support is the first step towards accelerated support for Mach32's,
+Mach8's, 8514/A's and other clones.
+<item>Colour depth greater than 8 on non-integrated controllers, where
+permitted by the hardware.
+<item>Mach32, Mach8 and 8514/A Draw Engines.
+<item>Hardware cursors where implemented by hardware.
+This has already been done for Mach64 integrated controllers.
+<item>TVOut, i.e. the ability to use a television screen as a monitor.
+<item>Motion Video, i.e. displaying an asynchronous data stream (TV signal,
+DVD, etc.) in a window or full-screen.
+<item>3D operations.
+</itemize>
+<sect>Reporting problems<p>
+If you are experiencing problems that are not already recorded in this
+document, first ensure that you have the latest current release of this driver
+and the Xorg X server.
+Check the server's log (usually found in /var/log/Xorg.0.log) and <htmlurl
+name="ftp://ftp.freedesktop.org/pub/Xorg"
+url="ftp://ftp.freedesktop.org/pub/Xorg"> if you are uncertain.<p>
+Secondly, please check Xorg's doc directory for additional information.<p>
+Thirdly, a scan through the comp.windows.x.i386unix and comp.os.linux.x
+newsgroups, the xorg mailing list archives at <htmlurl
+name="http://lists.freedesktop.org/mailman/listinfo/xorg"
+url="http://lists.freedesktop.org/mailman/listinfo/xorg">, and
+the Xorg bug database at <htmlurl
+name="https://bugs.freedesktop.org/enter_bug.cgi?product=xorg"
+url="https://bugs.freedesktop.org/enter_bug.cgi?product=xorg">
+can also prove useful in resolving problems.<p>
+If you are still experiencing problems, you can send <it>non-HTMLised</it>
+e-mail to <email>xorg@lists.fredesktop.org</email>.
+Please be as specific as possible when describing the problem(s), and include
+an <it>unedited</it> copy of the server's log and the xorg.conf file used.<p>
+<sect>Driver history<p>
+The complete history of the driver is rather cloudy.
+The following is more than likely to be incomplete and inaccurate.<p>
+Apparently, Per Lindqvist first got a driver working with an early ATI adapter
+under X386 1.1a.
+This original driver might have actually been based on a non-functional ATI
+driver written by Thomas Roell (currently of Xi Graphics).<p>
+Then Doug Evans added support for the ATI VGA Wonder XL, trying in the process
+to make the driver work with all other ATI adapters available at the time.<p>
+Rik Faith obtained the X11R4 driver from Doug Evans in the summer of 1992 and
+ported the code to the X386 part of X11R5.
+This subsequently became part of XFree86.<p>
+Marc Aurele La France took over development and maintenance of the driver
+in the fall of 1993 after Rik got rid of his VGA Wonder adapter.<p>
+<sect>Driver versions<p>
+Due to the introduction of loadable drivers in XFree86 4.0, it has become
+necessary to track driver versions separately.
+Driver releases use the following version numbering scheme.<p>
+Version 1 of this driver is the one I inherited from Rik Faith.
+This is the version found in XFree86 2.0 and 2.1.<p>
+Version 2 is my first rewrite of this code which only ended up being a
+partially unsuccessful attempt at generalising the driver for all VGA Wonder,
+Mach32, and early Mach64 adapters.
+Various releases of this version of the driver can be found in XFree86 2.1.1,
+3.1, 3.1.1 and 3.1.2.<p>
+Version 3 represents my second rewrite (although a rather lame one as rewrites
+go).
+Into version 3, I introduced clock programming for Mach64 adapters and merged
+in the old ati_test debugging tool.
+This is the version found in XFree86 3.2, 3.3 and 3.3.1.<p>
+Version 4 is a rather major restructuring of version 3, which became larger
+than I could comfortably handle in one source file.
+This is the version found in XFree86 3.3.2, 3.3.3, 3.3.3.1, 3.3.3.2, 3.3.4,
+3.3.5 and 3.3.6.<p>
+Version 5 is an almost complete restructuring of version 4 to fit in the newer
+driver API of XFree86 4.0 and later.<p>
+The introduction of version 6 is a first swipe at porting the driver to
+non-Intel architectures.<p>
+</article>