Will a PPU accelerate a CPU PhysX game?
Heh.. it was a golden question in Ageia times, with long discussion on official Ageia forums.
But in generally - Yes
, PPU can accelerate a CPU PhysX game, because it can run all PhysX SDK components (and even whole scene) in hardware (and GPU - only few, like cloth and particles)
Unfortunately, in non-PPU games difference was almost unnoticable, like +5 fps or so (not to mention, noone ever performed a wide test of this feature)
It's like Tony Carillo, Ageia marketing manager, told us finally:
We: Hey, does Gears of War use PPU ?
Tony: Yes, some physics calculations can be offloaded on PPU
We: Cool ! And what is the difference ?
Tony: You will not notice it.