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Old 07-01-10, 03:50 AM   #1
Nurbs
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Default GTX 295 (dual core) not working with two screens and compositing?

Hello,

I am trying to get my GTX 295 working with two screens (DVI and HDMI) connected and, for use with KDE's compositing features, the COMPOSITE extension enabled. The driver is Debian's 195.36. I did try a lot of things, but mainly:

1) Xinerama: I get Xinerama working, but this disables, as mentioned in the documentation, the COMPOSITE extension. Bad.

2) TwinView: I don't get this to work. I have used the examples from the documentation, manual setup and nvidia-xconfig (giving mostly the same configs), always ending up with the problem that the driver tells me that only one screen can be detected and TwinView will be disabled. In a way that makes sense, the other screen is recognized only by the 2nd GPU, but that means that TwinView can't work - or does it?

3) Single screen: works fine with either one and all acceleration, just not both at the same time.

Might I be doing something wrong (I am sorry that I don't have configs, I currently don't have access to the system) or is it a problem with that specific card (and possibly other dual GPU cards, too)? Does someone have a working config? Or was it fixed in the 256 drivers (could not find anything in the release notes)?

What I googled did not look too promising, other people did not seem to get it to work either.

Thanks!
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Old 07-01-10, 03:51 PM   #2
AaronP
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

For TwinView, the screens have to be connected to the same physical GPU, so that explains why it's failing to find another screen on the same GPU as the first one. KDE 4 has a bug (or maybe a conscious design limitation) that causes it to only work on a single X screen. If you want multiple screens with compositing, I'd suggest using GNOME (or basically any non-KDE4 desktop environment, for that matter).
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Old 07-01-10, 04:19 PM   #3
Nurbs
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

Thanks for the answer, even though I am not too happy about that. I'll abandon the idea of using Linux as a desktop system again once more and return to a VM.
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Old 07-03-10, 03:59 PM   #4
Artichoke1
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

Hi Aaron,

Any idea if/when rotatation of individual screens under TwinView will work? Or else when Composite will work under Xinerama?
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Old 07-03-10, 05:57 PM   #5
JaXXoN
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

Quote:
Originally Posted by Nurbs View Post
2) TwinView: [...] the other screen is recognized only by the 2nd GPU, but that means that TwinView can't work - or does it?
My understanding is that each of the two GPUs on the GTX295 is driving
a DVI output, so you can only configure separate X-screens, which will
work with Xinerama, but not with Composite in addition (as you already
experienced).

If you are willing to spend some extra money, then you may consider
the following solution:

1. Configure the GTX295 to operate in SLI mode
2. Attach a Matrox TH2G in order to drive up to three
1680x1050 LCDs or up to two 1920x1200 LCDs.
(LCDs need have the same resolution)

This way, you get the full performance of both GPUs and you could
enjoy a nice triple head setup :-)

regards

Bernhard


P.S.: alternatively, you could ask nvidia to provide SLI Mosaic
for the GTX295.
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Old 07-06-10, 03:18 PM   #6
Nephyrin
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

For what it's worth, I have a GTX 295 working with twinview, with the second GPU disabled. In fact, this is how X configured itself out of the box - without the 'MultiGPU' option in Xorg.conf, the second core just sits idle and GPU-0 drives both screens. Unless you're planning on playing high end games, a single core of a GTX295 should do just about anything to do with the desktop/compositing just as well for two monitors. The most intensive thing I do graphically in linux is play WoW, and that manages 60FPS on one monitor (with compositing enabled, no less) without the second core.

That said, the multi-monitor support in linux is pretty depressing - only proprietary driver hacks or a slow poorly supported extension... srsly?
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Old 10-10-11, 02:32 PM   #7
tuxiko
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Default Re: GTX 295 (dual core) not working with two screens and compositing?

I would like to know how to force a GTX 295 to disable one GPU, or to force one GPU to manage two monitors (one linked to a DVI port and one linked to the HDMI port), that is to only manage a single X screen, through TwinView.

Maybe by setting a specific parameter at nvidia module loading?

Nephyrin says that it was the default behavior at least with its driver when he posted the message (07-06-10). But it's not the case for the driver version 270.41.

(My problem is similar to the initial post with KDE 4.7)
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