Dual Screen with multiple graphics cards?

Question

Hi,
I have tried to utilise two screens, both to a seperate grahpics card but it does not seem to be working! Setting them as two different devices with BUS id's does not work and xrandr does not seem to be working either - it comes up that one of the screens is disconnected.
Here is my 60-radeon.conf:
   Section "Device"
       Identifier     "Advanced Micro Devices, Inc. [AMD/ATI] RS780L [Radeon 3000]"
       Driver        "radeon"
       BusID        "PCI:1:05:0"
EndSection
   Section "Device"
       Identifier    "Advanced Micro Devices, Inc. [AMD/ATI] Juniper XT [Radeon HD 6770]"
       Driver        "radeon"
       BusID        "PCI:2:00:0"
EndSection
And here is my xrandr command:
xrandr --output VGA-0 --auto --output DVI-0 --auto --right-of VGA-0
Any help would be greatly appreciated!

Answer 1

ElKatrina wrote:the X server crashes
It's my understanding that this should never happen, and always deserves a bug report upstream at xf86-video-ati or the X.org server.
What you can first try is installing xf86-video-ati-git from AUR to see whether it's already fixed and just not in a stable release yet.
The next step would just be collecting a stack trace and posting it on https://bugs.freedesktop.org/enter_bug.cgi?product=xorg in Driver/Radeon or so (only after looking whether ther is already a similar bug of course) depending on how the stacktrace looks.
You really want a second computer and do this with ssh because a paused X server that controls the keyboard/mouse and the tty is not something you want to deal with...
So you have an ssh server running and start X normally on your computer, then at the second computer you connect with ssh and attach gdb to the xserver with "sudo gdb /usr/bin/X $(pgrep -f /usr/bin/X)" or so. That will first pause the X Server and you have to "continue" with writing "c[enter]" or so. Then you do whatever you do to make it crash and when it is crashing, gdb will pause it again. Then you can get a backtrace with "bt[enter]". That will give you a list of function calls from which libraries lead up to the crash and possibly some extra information about parameters or so. Then quit with ctrl+d or "quit" or so.
If you get stuck on a black screen on the PC with the crashing X server, try "startx" over ssh and then killing it with ctrl+c again. Starting and killing X "properly" helped at least for me when that happened.
You can get a lot more information when you recompile some thing with debug symbols. For example if you have yaourt you can use yaourt -G xf86-video-ati-git to create a directory xf86-video-ati-git and download the PKGBUILD into it.
In the PKGBUILD you can add !strip to options so it looks like "options=('!libtool' '!strip')" and in the build() function anywhere before autoreconf/make add export CFLAGS="-O0 -ggdb" (and if there is c++ code, export CXXFLAGS="-O0 -ggdb", but for xf86-video-ati and the x server there isn't I think) and then simply reinstall with "makepkg -fi"
Now if you replicate the crash with packages with such debug information you can do "bt full" in gdb. Without these debug information you will just get a lot of "No symbol table info available." but with it you can get many variable values and function parameters that can help the developers greatly (possibly).