xref: /xsrc/external/mit/xf86-video-mach64/dist/README

  ATI Adapters README file
  Marc Aurele La France
  2002 February 12

  This is the README for the ATI Mach64 driver included in this release.
  ______________________________________________________________________

  Table of Contents


  1. Statement of intent
  2. A note on acceleration
  3. Current implementation for ATI adapters
  4. Current implementation of generic VGA support for non-ATI adapters
  5. xorg.conf specifications
     5.1 Driver ``ati''
     5.2 ChipSet ``name''
     5.3 ChipID & ChipRev specifications
     5.4 IOBase
     5.5 BusID
     5.6 Clocks
        5.6.1 Clocks for supported programmable clock generators
        5.6.2 Clocks for unsupported programmable clock generators
        5.6.3 Clocks for fixed clock generators on ATI adapters
        5.6.4 Clocks for non-ATI adapters
     5.7 Option ``nopanel_display''
     5.8 Option ``crt_display''
     5.9 Option ``noaccel''
     5.10 Option ``nolinear''
     5.11 Option ``HWCursor'' and Option ``SWCursor''
     5.12 Option ``SilkenMouse''
     5.13 Option ``shadowfb''
     5.14 Option ``dpms''
     5.15 Option ``backingstore''
     5.16 MemBase address
     5.17 Option ``ReferenceClock'' ``frequency''
     5.18 ClockChip ``name''

  6. Video modes
  7. Known problems and limitations
  8. Reporting problems
  9. Driver history
  10. Driver versions


  ______________________________________________________________________

  1.  Statement of intent

  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 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.

  The driver will provide

  o  accelerated support if an ATI accelerator is detected and the user
     has not requested that this support be disabled; otherwise
  o  accelerated support if a non-ATI 8514/A-capable adapter is detected
     and the user has requested such support; otherwise

  o  unaccelerated SuperVGA support if an ATI VGA-capable adapter is
     detected; otherwise

  o  generic VGA support if a non-ATI VGA-capable adapter is detected
     and the user has requested such support.

     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 ``xorg.conf specifications''
     section below for details.

  If none of the above conditions are met, the ATI driver will
  essentially disable itself to allow other drivers to examine the
  system.


  2.  A note on acceleration

  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.

  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.

  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.

  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.


  3.  Current implementation for ATI adapters

  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:

  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)


  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).


  The newer Rage 128 and Radeon chips are not 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.

  Adapters based on the above chips have been marketed under a rather
  large number of names over the years.  Among them are:

  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


  Also, a number of mainboards, laptops and notebooks harbour a Mach32
  or Mach64 controller.

  VGAWonder, Mach8 and Mach32 ISA adapters are available with or without
  a mouse.

  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.

  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.

  The driver does 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.

  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.

  On non-Intel platforms, the driver can, currently, only support PCI
  Mach64 adapters.


  4.  Current implementation of generic VGA support for non-ATI adapters

  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.

  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.

  The driver will enforce the following limitations derived from IBM's
  original VGA implementation:

  o  There can only be a set of four (non-programmable) clocks to choose
     from.

  o  Video memory is limited to 256kB in monochrome and 16-colour modes.

  o  Video memory is limited to 64kB in 256-colour modes.

  o  Interlaced modes are not available.

  o  Colour depths higher than 8 are not available.

  5.  xorg.conf specifications

  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.

  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.

  Other options affect the driver's operation once an adapter has been
  assigned to the ``Device'' section which contains them.


  5.1.  Driver ``ati''

  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.


  5.2.  ChipSet ``name''

  The default ChipSet name for this driver is ``ati''.  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.

  If ``ativga'' is specified instead, the driver will ignore any ATI
  accelerator it detects, but otherwise operate as if ``ati'' had been
  specified.  This specification ensures the VGA CRTC is used.

  A ChipSet name of ``ibmvga'' 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 ``ativga'' had been specified instead.

  A ChipSet name of ``vgawonder'' is equivalent to ``ativga'', except
  that only VGAWonder-capable adapters can be assigned to the ``Device''
  section.  This specifically excludes the newer integrated Mach64
  controllers.

  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
  ``mach32'' or ``mach64'', 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 ``ati''.

  On non-Intel platforms, only ``ati'' and ``mach64'' ChipSet values are
  operative.


  5.3.  ChipID & ChipRev specifications

  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.


  5.4.  IOBase

  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.


  5.5.  BusID

  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.


  5.6.  Clocks

  For the purpose of specifying a clock line in your xorg.conf, one of
  four different situations can occur, as follows.

  Those configuring the driver's generic VGA support for a non-ATI
  adapter, can skip ahead to the ``Clocks for non-ATI adapters'' section
  below.  Those not trying to configure the driver for a Mach64 adapter,
  can skip ahead to the ``Clocks for fixed clock generators on ATI
  adapters'' section below.

  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
  ``Clocks for fixed clock generators on ATI adapters'' section below.

  The two cases that are left deal with programmable clock generators,
  which are used on the great majority of Mach64 adapters.

  If you are uncertain which situation applies to your adapter, you can
  run a clock probe with the command ``X -probeonly''.


  5.6.1.  Clocks for supported programmable clock generators

  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.

  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.


  5.6.2.  Clocks for unsupported programmable clock generators

  This case is unlikely to occur, but is documented for the sake of
  completeness.

  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:

  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



  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



  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


  If the driver matches the clocks to the third setting above, function-
  ality will be extremely limited (assuming the driver works at all).


  5.6.3.  Clocks for fixed clock generators on ATI adapters

  This section applies to all VGAWonder and Mach32 adapters, and to
  early Mach64 prototypes.

  One of the following clocks specifications (or an initial subset
  thereof) can be used depending on what the adapter uses to generate
  dot clocks:

  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



  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



  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



  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



  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


  VGAWonder VLB, VGA 1024 VLB, Mach32 and Mach64 owners should only
  specify up to the first 32 frequencies.  Any more will be ignored.

  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.

  The order of the clocks is 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.


  5.6.4.  Clocks for non-ATI adapters

  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.


  5.7.  Option ``nopanel_display''

  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.


  5.8.  Option ``crt_display''

  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.
  5.9.  Option ``noaccel''

  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.


  5.10.  Option ``nolinear''

  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.

  On non-Intel platforms, the driver requires a linear aperture and, so,
  this option is ignored.


  5.11.  Option ``HWCursor'' and Option ``SWCursor''

  Option ``HWCursor'', which is the default, specifies that hardware
  facilities are to be used to paint the mouse pointer on the screen.
  Option ``SWCursor'' specifies that the mouse pointer is to be drawn by
  software, which is much slower.  If both options are specified, option
  ``SWCursor'' 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.


  5.12.  Option ``SilkenMouse''

  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.


  5.13.  Option ``shadowfb''

  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.

  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.


  5.14.  Option ``dpms''

  This option enables the driver's support for VESA's Display Power
  Management Specification.



  5.15.  Option ``backingstore''

  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.


  5.16.  MemBase address

  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.

  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.


  5.17.  Option ``ReferenceClock'' ``frequency''

  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.


  5.18.  ClockChip ``name''

  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 ``ATI 18818-0'' or
  ``ATI 18818-1''.  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 ``Clocks for unsupported programmable clock generators''
  above.


  6.  Video modes

  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.).

  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.


  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 "Native panel mode" that
  represents the panel's native resolution.


  7.  Known problems and limitations

  There are several known problems or limitations related to the ATI
  driver.  They include:


  o  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.

  o  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.

  o  Due to hardware limitations, doublescanned modes are not supported
     by the accelerator CRTC in 88800GX, 88800CX, 264CT and 264ET
     adapters.

  o  The ``VScan'' modeline parameter is only supported when using the
     VGA CRTC.

  o  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.

  o  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.

  o  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, xrefresh(1) 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.

  o  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.

  o  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.

  o  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.


  o  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.

     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.


     Support for the following will be added in a future release:

  o  Mach32's accelerator CRTC.  This support is the first step towards
     accelerated support for Mach32's, Mach8's, 8514/A's and other
     clones.

  o  Colour depth greater than 8 on non-integrated controllers, where
     permitted by the hardware.

  o  Mach32, Mach8 and 8514/A Draw Engines.

  o  Hardware cursors where implemented by hardware.  This has already
     been done for Mach64 integrated controllers.

  o  TVOut, i.e. the ability to use a television screen as a monitor.

  o  Motion Video, i.e. displaying an asynchronous data stream (TV
     signal, DVD, etc.) in a window or full-screen.

  o  3D operations.

  8.  Reporting problems

  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 https://www.x.org/releases/individual/
  if you are uncertain.

  Secondly, please check Xorg's doc directory for additional
  information.

  Thirdly, a scan through the comp.windows.x.i386unix and
  comp.os.linux.x newsgroups, the xorg mailing list archives at
  https://lists.x.org/mailman/listinfo/xorg, and the Xorg bug
  database at https://gitlab.freedesktop.org/groups/xorg/-/issues
  can also prove useful in resolving problems.

  If you are still experiencing problems, you can send non-HTMLised e-
  mail to  <mailto:xorg (a] lists.fredesktop.org>.  Please be as specific as
  possible when describing the problem(s), and include an unedited copy
  of the server's log and the xorg.conf file used.



  9.  Driver history

  The complete history of the driver is rather cloudy.  The following is
  more than likely to be incomplete and inaccurate.

  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).

  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.

  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.

  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.


  10.  Driver versions

  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.

  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.

  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.

  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.

  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.

  Version 5 is an almost complete restructuring of version 4 to fit in
  the newer driver API of XFree86 4.0 and later.

  The introduction of version 6 is a first swipe at porting the driver
  to non-Intel architectures.

  -----------------------------------------------------------------------

All questions regarding this software should be directed at the
Xorg mailing list:

        https://lists.freedesktop.org/mailman/listinfo/xorg

The primary development code repository can be found at:

        https://gitlab.freedesktop.org/xorg/driver/xf86-video-mach64

Please submit bug reports and requests to merge patches there.

For patch submission instructions, see:

	https://www.x.org/wiki/Development/Documentation/SubmittingPatches