Using two dual-head Radeon cards with X on a single PC with 3 monitors

Jan Kasprzak kas at
Mon Aug 22 06:09:01 PDT 2011


Mark Cave-Ayland wrote:
: I'm currently struggling trying to setup one of our new PCs with 2
: dual-head Radeon cards and was hoping that someone here could help
: me out a little. The OS is Debian squeeze (Linux) running a 2.6.39
: backports kernel.
: Independently these appear to work absolutely fine. Now the problem
: is when I try and run them both together. If I launch them as 2
: separate X servers like this:
: Xorg -config /etc/X11/xorg.1.conf :1
: Xorg -config /etc/X11/xorg.2.conf :2

	Shouldn't the -isolateDevice be used in order to avoid
the X servers disabling the other card? Also you may want to make
them share a common VT (although I am not sure if this is necessary
in dual-head setup as opposed to dual-seat). In my dual-seat desktop,
I use the following command lines:

X :0 -layout Primary -isolateDevice PCI:1:0:0 vt7
X :1 -layout Secondary -isolateDevice PCI:5:0:0 -sharevts vt7

(the -layout option is analogous to your -config, but allows you to share
a single xorg.conf file for both X servers).

	However, I had problems with my multi-seat desktop with 2.6.39
and newer kernels, so you can also try to downgrade the kernel. 2.6.38
works for me. FWIW, the Fedora bug report I have filled is here:


| Jan "Yenya" Kasprzak  <kas at { - work | - private}> |
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