Information for Alliance Promotion chipset users
  Loic Grenie ( <mailto:grenie@math.jussieu.fr>), Henrik
  Harmsen ( <mailto:Henrik.Harmsen@erv.ericsson.se>)
  6 March 2000
  ____________________________________________________________

  Table of Contents


  1. Support chipsets
  2. Acceleration
  3. DGA
  4. Video
  5. Shadow framebuffer
  6. Configuration
  7. glide2x
  8. Questions


  ______________________________________________________________________

  1.  Support chipsets

  The apm driver in the SVGA server is for Alliance Promotion graphics
  chipsets. The following chipsets are supported:


  o  6422

     Old chipset. The driver is still very unstable and has computer
     crashes. You should use XFree86 3.3.x for this chipset.


  o  AT24

     As found in Diamond Stealth Video 2500. Quite similar to AT3D.

  o  AT25, AT3D

     AT3D is found in Hercules Stingray 128/3D. Most other Voodoo Rush
     based cards use the AT25 which is identical except it doesn't have
     the 3D stuff in it.


  2.  Acceleration

  The apm driver uses the XAA in the SVGA server. It has support for the
  following acceleration:


  o  Bitblts (rectangle copy operation)

  o  Lines (solid, single pixel)

  o  Filled rectangles

  o  CPU->Screen image transfers.

  o  CPU->Screen colour expansion (text accel).

  o  Screen->Screen colour expansion (cached text accel).

  o  Mono 8x8 pattern fill. Not for 6422.

  o  Colour 8x8 pattern fill (in 8bpp). Not for 6422.

  o  Hardware cursor.

  o  Pixmap caching.

  All in 8, 16 and 32 bpp modes. In 24bpp mode only Bitblts and Filled
  rectangles is supported. Also VESA DPMS power save mode is fully
  supported with "standby", "suspend" and "off" modes (set with with the
  "xset dpms" command).


  3.  DGA

  Full DGA 2.0 support with framebuffer access and drawing acceleration.


  4.  Video

  It has limited hardware support for video decoding on the AT24 and
  AT25/3D. It can also display an image in YUV colours inside the
  desktop. There are some more exotic formats such as YUV 4.1.1, YUV
  4.0.0 and RGB 8,16.32bpp.


  5.  Shadow framebuffer

  There is a mode, called shadow framebuffer, where the graphics are
  used to display the images. All rendering is done in memory in a so-
  called shadow framebuffer. This mode is useful if you need lots of
  reading in the video memory and to use it you will have to put

    Option "ShadowFB"



  in your xorg.conf file.


  6.  Configuration

  You can turn off hardware cursor by inserting the following line in
  the Device section of the xorg.conf file:

    Option "SWcursor"



  Or turn off hardware acceleration:

    Option "noaccel"



  Or turn off MMIO


    Option "nolinear"



  Do not specify either the amount of video RAM or which chipset in the
  config file. It is better to let the driver probe for this. Also don't
  put any "clocks" line in the device section since these chips have a
  fully programmable clock that can almost take any modeline you throw
  at it. It might though fail at some specific clock values but in that
  case you should just try a slightly different clock and it should
  work.


  7.  glide2x

  There is support for the XF86Rush extension for use with the glide2x
  library.


  8.  Questions

  Any questions regarding this driver should be sent to Loic Grenie. It
  should be possible to add support for the 3210 chipset if someone
  needs it.