               Information for Alliance Promotion chipset users

 Loïc Grenié (<grenie@math.jussieu.fr>),       Henrik Harmsen (<Henrik.Harm-
                            sen@erv.ericsson.se>)

                                 6 March 2000

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 fol-
lowing 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 rectan-
gles 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

First: Run the xorgconfig program to create a correct 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 pro-
grammable 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 Loïc Grenié. It should
be possible to add support for the 3210 chipset if someone needs it.

     $Id$


$XdotOrg: xc/programs/Xserver/hw/xfree86/doc/README.apm,v 1.3 2004/09/03 23:41:21 kem Exp $
