Physx doesn't run on AMD hardware and you need
Link
To make the AMD+Physx Nvidia card to work.
Or a motherboard with the Hydra chip from LucidLogix.
Some MSI and ASUS motherboards got it, dont know about other brands.
PhysX doesn't work slower, its just that you get no support if it doesn't work or is glitchy.
I'd rather learn OpenCL than CUDA, because locking your project to cater one GPU brand isn't a smart move,
Marked share.
http://www.xbitlabs.com/images/news/2010...3_2010.png
Valve Announce 25 Million Users For Steam
Now according to hardware survey
Hardware
Now cutting the game the way that 32% of 25 million users will not be able to access.