I have added a second 7900GT to my system, and am able to switch in the nvidia control panel to SLI, which runs fine and stable, not even too hot. But, when I ever reboot, I get a blue screen with "IRQL_NOT_LESS_OR_EQUAL". I have to go to safe mode and unload the nvidia drivers (93.71 forceware for win XP) and restart, to get out. If I change out of SLI before I reboot, everything is fine.
I have upgraded the drivers, checked the connections, etc.
ASUS P5N32-SLI SE Deluxe, 7900GT (one sparkle other evga), Antec Trio 550, 2 GB RAM, 2 HD, 2 DVD/RW. Win XP.
I have that same board in my case right now. I'm exchanging it for an EVGA 680i SLI board. I've had enough of that board to last me a lifetime. I've reloaded windows twice on that board to try and fix the SLI issue I was having with 2 7900GTs. The NForce 4 is the culprit I would think. I get weird performance in SLI and I've tried everything. Good luck man. I'm sorry to report this negativeness to you lol. Maybe you'll have better luck then me.
You have an incompatability problem with a piece of hardware, or you have bad drivers somewhere. First thing I would do is go into the control panel and remove all the nvidia drivers for your video cards. Then go upto the device manager an delete your video cards. REBOOT. When the machine restarts, it will tell you it found new hardware. ( your video cards )....Don't let windows try and install any drivers or anything. It will then tell you that something happened and new hardware might not work properly. That's okay.
Now, goto nvidias' website and get the 91.34 or earlier drivers. Download and install. REBOOT. See if that helps.
Otherwise, you'll have to start unplugging hardware til you find out whats causing problems.
While you up in the device manager, check and see if anything else needs to be updated. One thing can mess up your machine.
Do you have the SLI link attached correctly? Also try removing the second card and downloading the lastest drivers as others said. That should fix the problem. Otherwise try the new card on its own to see if its damaged or not, because that is probably it. If none of those work, I see nothing else you can do but reinstall windows
I have tried older drivers but no luck. Both cards work on their own. The bridge I can't tell, but again, SLI works on the system: it just crashes when it reboots, not after the BIOS runs, but right after the windows screen starts to load. I called ASUS, and they say it could be that the P.S. is too weak, but this doesn't seem to be reasonable by my calculations and the nVidia suggestions.
I guess I'll try and reinstall windows, but it's such a pain .
Since the video cards are not made by the same company, that could be the problem.
He's right, you need two of the exact same card to sli them. you might be able to get away with running them in tandem, but I doubt that would work even if you reinstall windows. Though something that might work is if you change the bios settings so that they are clocked exactly the same, that might fool your motherboard into thinking they are the same card
Thanks to all, gave up after the windows reinstall didn't help (which itself is not much fun when you have to fit the nvidia RAID drivers in somehow, believe me). Card returned, and may ASUS and nVidia get what they deserve.