Ubuntu
xorg-server package

  1. Bug #316514
  2. Comment #21

Comment 21 for bug 316514

Revision history for this message
Rudolf Cardinal (rudolf-pobox) wrote : Re: MASTER: Xinerama/Multihead with several video cards is not supported

I hope this is the right bug to add to; apologies if not.

My problem is: Xorg 1.9 can't do a single seamless desktop with two video cards without Xinerama.

I'm running Ubuntu 10.10 (Maverick) on a Asus P5N32-SLI motherboard with two NVidia GeForce 7600GS video cards (these are NV40-class cards as seen by Nouveau) through PCI. Each card is connected to a (rotatable) monitor, as it happens via DVI. My sequence of problems has been:

1. Current binary NVidia drivers for Ubuntu 10.04 allowed (with Xinerama) the left monitor to run in landscape mode and the right monitor in portrait mode (using ' Option "Rotate" "CCW" ' in the Device section of xorg.conf). However, they caused intermittent machine lockups (variably but including nothing-working crashes, including keyboard LEDs and kernel SysRq magic keys). Machine effectively unusable. So, out with NVidia drivers (except that their removal left the machine unbootable, so on to Ubuntu 10.10 and nouveau).

2. The Nouveau drivers reject Option "Rotate" ("(WW) NOUVEAU(1): Option "Rotate" is not used" in /var/log/Xorg.0.log).

3. Xinerama allows a seamless desktop, though without the ability to rotate one monitor. However, it crashes a bunch of apps at present; see bug https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/650539 . So Xinerama is (currently) out of the question, and, as I understand it, is deprecated in any case.

4. Creating two {Device, Monitor, Screen} sets of descriptions in xorg.conf, and stitching them together in the ServerLayout section [Screen 0 "Screen0" 0 0 / Screen 1 "Screen1" RightOf "Screen0"], allows two video cards with two monitors to be used. Great! And running "xrandr --screen 1 --output DVI-I-2 --rotate left" from a new file /etc/X11/Xsession.d/45custom-xrandr-settings allows the right-hand (second) monitor to go into portrait mode automatically following first login to X.

5. However, in this configuration there are two X screens, each with its own taskbar, and windows can't be dragged between screens, although the mouse pointer can wander between them. Presumably this reflects the problem of "one pool of memory per graphics card" described above, as other web sources suggest that a seamless desktop is easy to create on "dualhead" or similar (>1 output from a single video card) systems.

6. So, upshot: Xinerama is deprecated and now makes things crash, but X.org 1.9 with XRandR 1.3 doesn't seem able to create a seamless desktop across two video cards.