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I've a radeon r9 270x with four outputs, two DVI, one HDMI and one DisplayPort output.

I'd like to configure the X server such that it has two screens, from a user's point of view it should provide DISPLAY 0.0 and 0.1.

I tried with two Monitor, two Device and two Screen sections in /etc/X11/xorg.conf. This works if I don't specify "Screen" explicitely in the Device section but then I end up with a single Screen (DISPLAY=0.0).

I tried to explicitely set the Screen number in the screen section (like below) but this didn't work.

If I select Screen number 0 for the first Device Section and Screen number 1 for the second Device section then the X server starts, but from /var/log/Xorg.0.log it see that the X server tries to use the DisplayPort and HDMI outputs which are not connected.

I I select Screen numbers 2 and 3 in the Device sections then the X server refuses to start.

Section "Device" Identifier "Device0" Driver "radeon" # Screen 1 # doesn't work EndSection

Any ideas how to get a dual screen set up with the radeon driver?

This is debian unstable, Kernel 4.3 if it matters.

migrated from serverfault.com Jan 31 '16 at 21:38

This question came from our site for system and network administrators.

  • Did you try creating your ideal setup with xrandr on a running X server? (If you succeed in that, you can simply add an xrandr command to your environments startup applications that sets your screens up. Might not be as pretty as configuring xorg directly, but same result) I've commonly found xrandr easier to deal with than xorg configuration files for this kind of thing. – Cestarian Feb 1 '16 at 0:47
  • Did you ever find a solution to this? My scenario looks identical to yours as described. – ToBeReplaced Feb 13 at 5:20
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Try creating a ServerLayout section for the screens. Do not edit the device section, just add this to your conf file.

Section "ServerLayout"
    Identifier     "DefaultLayout"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" LeftOf "Screen0"
EndSection
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I don't think what you want is possible, at least in the way you're wanting to go about it.

The Screens in xorg.conf aren't the same as additional displays. DISPLAY=0:1 means the second X server on the machine, not the second screen.

Someone correct me if I'm wrong, but I don't think two X servers can share a single video card, no matter how many outputs it has. To do that, you use Xinerama.

There is the xnest server that might be usable for this, but I have no experience with it so I'm not sure if you can do what you want with it. In theory, you might be able to convince your window manager to use the first screen and run xnest fullscreen in the other - but I'm only speculating here.

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