Problems with X.org and ATI Radeon

[Falko Schmidt <kaethorn@stud.uni-stuttgart.de>]

Here I present some of the problems I encountered on the way to a
dual head setup using the Xinerama or MergedFB extensions of the
Xserver. I was using Debian/alpha testing and/or sid.

Since X.org was in Debian, I've been having trouble with my ATI graphics
cards (Radeon 7500 and Radeon 9250). They've been working fine under
XFree with the following setup:

 * using both heads in xinerama without dri
 * using only one with dri

Now using a self-compiled X.org X11R6.8 I can have

 * both head in MergedFB with dri

However with  X11R6.9 it turned out that

 * MergedFB AND dri will lock the machine up immediately.
 * MergedFB without dri but with RenderAccl will work about at about 30%
   of the tries. The rest of the time the Xserver falls into an endless
   loop printing "(EE) RADEON(0): Idle timed out, resetting engine...".
   The process of Xorg takes up all the CPU, the screen in blank. If I
   kill -9 it and start it up again, the machine locks up.
 * with Xinerama instead of MergedFB and with RenderAccl enabled, I get
   the same result.
 * with Xinerama enabled and RenderAccl "false" however, the Xserver
   starts but is unusably slow (e.g. scrolling down in a browser takes
   5 secs).

With X11R7.0 i get

 * no warning, not output but no screen either. After some seconds the
   screens switch off but don't return to the console. Logging in
   remotely I can kill -9 Xorg. But upon restart it would lock up the
   machine.

Well, I hope I didn't miss any test case. Furthermore I didn't really
test all the cases with both the 7500 and 9250. I used the latter one
most of the time. It also didn't matter whether I used a 32bit or 64bit
PCI slot.

I would really like to use two screens, preferably with dri support
because I'm developing an OpenGL application. Unfortunatly it seems
that the ATI drivers won't do their job well and alternatives like
Matrox G400+ with two heads seem to work even worse.

Can anyone point me to a solution? Are there people who use both heads
of a Radeon on alpha and can feed me with some insight on how to make
it work?

Any help would be greatly appreciated.

Kind regards,

Falko Schmidt