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Old 06-21-10, 10:47 AM   #1
jrtroberts
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Default 2 video cards with linux/ 2 twinviews

I am working with a system that uses two video cards.
OS = ubuntu 9.10 x86_64
one is an onboard Quadro FX 470
the second is an EVGA Geforce 9500GT

I am having issues getting the video cards to work properly.

The goal: 4 monitors, two from each video card.
each pair of monitors = 1 X screen.
quadro fx 470 = x screen 0 - two monitors
geforce 9500gt = x screen 1 - two monitors

I would like to enable twinview on each card.
The problem I am having is that, while twinview does provide me with 2 large virtual desktops, my applications maximize across both. The same goes for my desktop, the applications menu is on primary monitor and the other side of the panel with the shutdown and clock is on monitor 2.

After asking in the freenode irc channel #nvidia, I was told that xinerama may not currently support this type of usage. That the driver is only able to communicated one twinview arrangement at a time.

Can anyone confirm this for me, or offer me a solution?

I have stopped trying to implement 2 twin views because it is too hard to work with the split screen effect. I am currently running 4 Xscreens.
Here is my current xorg.conf configuration. It has commented out configurations from the twinview attempts, done by nvidia-settings automatically.
http://pastebin.com/UVe8Xs6m



Please let me know if what I am trying to do is possible with my current hardware/drivers
Thank you.

joshua
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Old 06-28-10, 04:45 PM   #2
AireTamStrm
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Default Re: 2 video cards with linux/ 2 twinviews

What window manager are you running?
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Old 06-29-10, 02:25 PM   #3
sniff
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Default Re: 2 video cards with linux/ 2 twinviews

Hello,

I have tried the same setup. 2x twinview on four monitors works the same for me as it has for you. Windows maximise over two screens instead of to one. I currently use 4 separate X screens joined by xinerama. This works ok but is a little bit slow. I am using a GT220 and a 9500GT. I have been thinking about upgrading to two GTS250s to see if that speeds things up.... not sure if it will. I don't think there is a better solution. Unless you want to wait for ATI Eyefinity which might be...

Cheers,
Phil
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Old 06-29-10, 06:31 PM   #4
etherfish
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Default Re: 2 video cards with linux/ 2 twinviews

The problem has to do with the XINERAMA protocol extension. You can verify what XINERAMA configuration is being conveyed to your window manager by running:

xdpyinfo -ext XINERAMA

When you use twinview alone, the NVIDIA drivers provide an XINERAMA extension that reports the physical layout of the screens. However, once you enable the xorg xinerama extension, it reports only the virtual geometry of the whole twinview display. In the past, I recall having success using the "TwinViewXineramaInfoOverride" option described in Appendix B.
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Old 06-29-10, 06:36 PM   #5
JaXXoN
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Location: Munich
Posts: 910
Default Re: 2 video cards with linux/ 2 twinviews

Hi!

That's a known limitation: the very moment "true" Xinerama is
enabled (because of two video cards), then the "faked"
Xinerama extension of the nvidia driver is disabled.

There are a number of patches available where you can
set the XineramaInfo to arbitrary values, i.e. this one:

http://www.nvnews.net/vbulletin/showthread.php?t=85604

However, the problem is that this solution requires patching
and re-compiling parts of the X-server, which might not be an
easy task for most common users. (also, i'm not sure if
there any patches around for the recent Xorg releases).

In general, Xinerama has a number of limitations, i.e. it
is sort of incompatible with the composite and randr
extensions (required for Compiz). Apart from other
software bugs, two cards in one PC are always a source
of problems, i.e. PSU breakdown or overheating.

For this reason, I switched to another hardware solution
that allows to run six LCDs up to 5040x2100 (2x3x1680x1050)
or four LCDs at 3840x2400 (2x2x1920x1200) from a single
graphics card:

http://www.nvnews.net/vbulletin/showthread.php?t=126134

However, this variant isn't cheap ...

regards

Bernhard
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