Solved / FYI: SLI w/ Asus 2 x 7600GT, P5N32-SLI Deluxe Linux 2.6.18 (crash 2.6.16/17)
This is just for your info:
In a new system, I wanted to use two nvidia Asus 7600GT Silent 256MB DVI PCI-E cards in an Asus P5N32-SLI Deluxe motherboard (nvidia nForce4 Intel x16 Chipset) in SLI mode. As I don't have Windows XP, I couldn't test that.
(1) I observed dark screens afater booting on both win2k and X11 (this problem actually remains, will open another thread)
(2) Whenever I tried to use X11 in SLI mode, an immediate crash was the consequence (after 0..30 seconds, either on X11 startup or when OpenGL window used, but definitely when using nvidia-settings to review OpenGL parameters / check for SLI setup recognized).
This happened for XFree86, and Xorg 7.0.0, using the latest nvidia driver 8762, across various linux versions (if I remember correctly: maybe 2.6.8/2.6.11?, but quite certainly: 2.6.16, 2.6.17), no matter which SLI mode I actually used.
But single monitor and twinview setups without SLI would work, even with 2 monitors on two cards and OpenGL-windows that could be moved across the monitors.
The problem has now disappeared after I have moved to kernel 2.6.18-rc3. After I managed to compile/install the 8762 driver with this kernel, I tested SLI - expected another crash, but was surprised that it actually worked smoothly - long enough to complete viewperf or to work with the software for which I prepared the setup, in all SLI modes.
Remaining issues where some artefacts in testing software like the lower screen part black in SFR mode (e.g. in tuxracer, euphoria), or lack of vsync heeding in AFR mode (euphoria) or similar things -> most avoidable by chosing another SLI mode.
I read in another contribution that using kernel paramter pci=conf1 was advised to and helped another user - maybe, kernel 2.6.18 also changed something with this respect and that's the reason why it worked for my setup since then.
Hope this info can help someone; I myself have spent a lot of not-so-happy time for that those days,
Good luck, Joerg