Alright so I've been using 2 EVGA 9800GTX+'s for the past couple months in SLI mode and they've been working perfectly until a week ago when my FPS in my games started to decrease dramatically. COD4 went down from 150 to 33 fps and L4d went down to 30. I reinstalled the display drivers countless times, cleaned the display driver registry, made sure the cards are connected correctly, switched the SLI bridge, set up SLI correctly and reinstalled the games with the latest patches. I don't know what else to do besides maybe buying the next step up in the 200 series. I emailed NVIDIA for help and that didn't work at all. My system is Vista ultimate 64, 8GB RAM, Intel Core 2 Quad Core 3.15 OC, EVGA 780i FTW motherboard, 750W power supply. My case has excellent cooling (Coolermaster HAF). Any help would be awesome, and none of the cards are OC.
Some diagnostic steps that you might take to find out the cause:
0) Run all your antivirus softwares for obvious reasons.
1) Run some benchmark software (eg 3DMark06) to get a score with SLI enabled. Score=?
2) Run again with SLI disabled. Score =?
3) Compare these scores with other similar systems which you can google in the net. I think Futuremark website has a large database. How are they compared?
4) Unplug 1 card and with just 1 card in the primary slot, run 3DMark06. Does it get a proper score for a typical 9800GTX+ ?
5) Repeat with the other card. Does it get a proper score too?
Have you installed any hardware or software recently?
Are the power cables to the 2 cards plugged in all the way?
Of course, the last thing is to reformat your harddrive and reinstall the OS. But this should be your last resort.
I figured out the problem, it was an older version of Direct X 10 that was installed when I installed Phantasy Star Universe. Now I have my original FPS rate back and performance in games as well. But I figured it out after I reinstalled my OS...