The skinny on SLI and Physx?

I run a system with 2 GTX 260 core 216s with SLI and GPU physx enabled and I have a couple questions. One, since these are identical cards are they sharing the workload for physx and graphics? Two, is it better to do this rather than having the CPU dealing with physx (PII 940BE@3.4ghz)? Obviously the cards are more capable because of the far greater parallel processing, but how much does this take away from graphics processing and, as a result, frame-rates?

Basically, if anyone could point me toward a relevant knowledge base or share some experience it would be greatly appreciated, as I'm having some trouble figuring out exactly how this stuff works.

If you are running at 19X12 res or below I dont honestly think you will see much of a difference running with PhysX on or off UNLESS the title actively uses it. There are very few games out there that make use of PhysX and honestly I think its going to stay that way. Programmers do not really want to write programs specifically for one thing like PhysX. I think over time we will see a move toward OpenCL based physics as both ATI and Nvidia can make use of it.

If you let your CPU do PhysX, no matter if it's 3Ghz or 7, FPS will go single digit. Trust me, I've been testing it.

Also, PhysX will only be used in games that support it. So if the game does not (such as any Valve game, HL2 etc), there would be no difference turning PhysX on or off.

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