Originally Posted by cadaveca
For me, memory bandwidth plays a large role in Multi-GPU performance, and in a very perceptible way. I agree with your sentiment about memory perforamnce in a big way for everything else though.
I tested out memory last night in 3dMark Vantage and 3dMark 11. With 2 7850's and 3770K at 4Ghz (Z77 Mpower), my scored dropped 100 points in 3d11. In vantage it dropped a few hundred. Here is the thing though, in BOTH tests, it lost those points because of the CPU and PhsyX tests. The GPU scores remained the same.
For games, in BF3 and batman, I saw negligible differences (1FPS). So at least with these lower powered cards, it doesnt make a difference at all. I will have 7970's on the test bench here in a few days, and will try that again.