http://forum.needforspeed.com/eaforum/posts/list/313448.page
"anyone with an nvidia card that can enable physx can test this
open nvidia control panel, enable physx if not enabled already, on top line click 3d setting and tick show visual indicator(this is avaible in latest beta drivers not sure about earlier), start shift and u will see physx - cpu. now to check its not a driver but u need a game that delinatly uses gpu physx for me i checked with the batman demo as soon as it starts physx - gpu is shown
now from what i rem the devs said that gpu was used for some and cpu for others ,well ive spent 2 hours test different tracks and different cars and the indicator never changes"
Lucky for me, the NFS Shift runs fine with my hardware, at 1280x1024, 8xFSAA and everything maxed, I never experience FPS below 42fps. I found out that setting Catalyst AI to Advanced fixed the slow down issue that I had in that game. Even I disabled my PPU and the framerate didn't change at all, here's the link for nVidia users to test it and prove that NFS doesn't use GPU acceleration of PhysX. But it has been acknowledged that ATi has issues with that game, that it has nothing to do with PhysX but the fact that the game isn't using the ATi's hardware resources properly.
PS: My brother's in law HD 3870 can max the game with no FSAA and his FPS never drops below 27fps and is running at 1280x1024 and he doesn't have a PPU or nVidia GPU for PhysX.
A proof:
http://www.youtube.com/watch?v=-aRfa_4HlT0 <<A video of the gameplay in my computer, running at 1280x1024 with everything maxxed plus 8xFSAA and 16xAF and Catalyst A.I set to Advanced.