I've got two GTX 275's in SLI and I've noticed that the GPU Usage of both GPU's only go up to 50% (measured with EVGA Precision). When I disable SLI, one GPU reaches 100% usage and I get the same fps compared to SLI.
The games I've tried are: Resident Evil 5, Crysis. Crysis Warhead, Metro 2033, Bioshock, Battlefield Bad Company 2, Risen and Call of Duty Modern Warfare 2.
Hey you can try this cuz i had the same issue with my 9800 sli
SLI will work without the connector and you might have to get a new one
Basically the connector keeps the cards inSync
SO go to device mgr
select display and disable the second card, and then enable it.
do the same with the first card and then re run your test.
I had to do this only after restarting my computer. If I turned it off and waiting a few minutes then start it would work normal
To this day I still have no idea why it does that but the only solution I found was the disabling of the display