Originally Posted by brunner
Physx is always faster if you put it on a seperate card. Even with Quad-SLI, it's better to have a 5th card for Physx. For some reason, there's a huge performance impact when Physx isn't offloaded to a GPU that is just dedicated to it.
I saw a benchmark on Guru3d that showed virtually no difference between 480's in SLI and the same with a 280 for Physx:
And here is a single 480 with and without a 240 for Physics:
Finally a 470 with a 240:
I'd say a dedicated Physix card isn't needed with the 400 series, unless you just happen to have one laying around. I certainly wouldn't buy a card just for Physx.