The question is, if I were to build a rig with an ATI setup for graphics, would I be able to install an older 8800 (or 9800, whatever) Nvidia card for use as just a dedicated PhysX driver? This is a matter that's been bugging me for a little while now. If this question's already been asked here, I apologise for the repeat in topics.
You would need to run both Nvidia cards in order to use the 2nd gpu as a dedicated physx card. Using physx this way is a combination of both the hardware and the driver, so you wouldn't be able to do this with the ATI card.