Ubuntu – Nouveau quad monitors dual-GPU error: could not set the configuration for CRTC 64


I have 2 GPU (Nvidia G96GL Quadro FX 580) hooked to 2 monitors each, and while I was on 12.04 I was happily using all 4 monitors using the proprietary drivers.

I recently upgraded to 13.10 and all hell broke loose.

  1. using proprietary drivers, the most I can get is 2 monitors under TwinView
  2. the moment I enable Xinerama and separate X-screens, I end up with a black screen on restart. No amount of tinkering with xorg.conf has been able to get me any further.
  3. I reverted to Noueaou, and I am happily able to use 3 monitors now. Any 3 but never 4 at a time, as the fourth one, although detected, is always disabled.
  4. If I try to enable the 4th monitor, I get two popups with the following messages:

    "The selected configuration for displays could not be applied", "could not set the configuration for CRTC 64", "Failed to apply configuration: %s",  
    "GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._gnome_2drr_2derror_2dquark.Code2: could not set the configuration for CRTC 64"

That's where I am stuck after a week. Tried all sorts of proprietary drivers, all sorts of instructions etc but I feel the only way to get back my 4th monitor is to downgrade to 12.04 and hope 14.04 doesn't mess up things. Anyone to help?

Best Answer

The Nouveau driver has problems with supporting 4 monitors in a dual GPU configuration:

I would avoid those if possible. Both nouveau and the nvidia driver wil support them in a 4-monitor configuration, but there will be issues, esp with nouveau. Not sure about nvidia.

If possible, get a Kepler-based card, which can drive 4 CRTC's from 1 GPU. That way you get none of the trouble.

There are 2 ways of dealing with that (neither is nouveau-specific):

(a) You can use PRIME to render on one GPU and use the outputs on the other gpu to display said rendering. This is possible using xrandr 1.4 and Xorg 1.14.3 or later. (b) You can use Xinerama to create a virtual screen on these. This loses you xrandr and direct rendering.

Neither of these yields a particularly fast experience

And freedesktop say:

Multi-monitor desktop with Nouveau

If you have a single graphics card (GPU) with multiple heads, it should all just work for you with RandR 1.2 and offer full (whatever is implemented) graphics acceleration. If you really want multiple SCREENs on a dual-head card, there exists the experimental configuration option ZaphodHeads.

If you have multiple graphics cards, the only way to combine them into a single SCREEN is the Xinerama feature, and all the drawbacks listed for it apply. Notice, that a card with multiple GPUs counts as multiple cards. The end result depends on which outputs are driven by which GPUs.

Conclusion: it may be possible to get Nouveau quad head on two GPUs to work with some particular configuration, but it has not been well tested, and performance will not be optimal. The suggested option is to upgrade to a single GPU card that supports multiple monitors (either Nvidia or AMD Eyefinity 6; AMD has the advantage of official open source driver support).