Xinerama, Compositing, and the Ways in Which I Hate Them

[Fate]

Here's a brain tickler for you.

Windows pissed me off for the last time the other day and I wound up blowing away my hard drive and setting up dual booting between WinXP (games) and Ubuntu (everything else).

I have two monitors, and I have two GeForce 7950's. In Windows World I SLI them together for games. The rest of the time, I run dual monitor. In Windows, the Nvidia driver wants one monitor plugged into one card and the other monitor plugged into the other to run multimonitor.

So far, so good.

It took a bit of fiddling but I got Linux to recognize the second monitor on the second card (initially the Nvidia config applet thought there was no monitor on the second card) via some xorg.conf fiddling. But, because the Nvidia driver for Linux is apparently fucking retarded, you can't use Twinview across two monitors on two cards, even if the cards are identical and connected with a fucking SLI bridge. The best I could do there was running two X sessions, one on each monitor (I didn't even know you could do that...) which doesn't allow moving windows between monitors.

So I tried using Xinerama, which was actually relatively painless to get working across the two cards, and dual monitor works exactly as advertised.

Except. Compositing (comiz) doesn't work.

When I was running one monitor on one card it worked fine. When I was running two X sessions it worked fine. In Xinerama? Nada.

OpenGL acceleration works on both monitors, GLXGears works, games work, video acceleration works, etc. But not compositing, even when I have it explicitly enabled in my xorg.conf.

Is this even possible? At the moment I have a couple of options...

- Run two X sessions again (annoying).
- Use Twinview, and plug my second monitor into the first card, ignoring the second... And switch back every time I go into Windows.
- Ditch those 7950's and get a GeForce 8800, you idiot.
- Live with lack of Compiz (what's the fun in that)?
- Learn some magic combination of settings to make this work.

Ideas?

[Fate]

Okay, I got this working. Eventually. The solution was to just plug both monitors into the same card. Under the new nVidia drivers in Windows it is apparently possible to run dual-head from one card in a 2 GPU system again. Evidently this feature was removed in the previous version of the drivers I was using before I reformatted, which I think were 176.16.