Can I have two different models of (Nvidia) video cards on one system, one for video and one for Physix (not sure if I spelled that correctly)? If so, do they have to be linked via SLI?
Unless things have changed since I did it with the 400-series cards, SLI requires the same model of card to work.
You can use different models as long as you are using the other card for Physx and aren’t planning on using SLI. And you won’t need an SLI bridge.
However, given the handful of games that support Physx, and given that most single mid-range cards can handle those physx effect fairly well, I would absolutely not recommend you buy another card just for physx.
Going SLI would get you much better performance, or sticking to a single mid-range or high end card should handle the Physx effects just fine.
From their FAQ: