Originally developed by Ageia, PhysX is a propietary real-time physics engine middleware. NVIDIA bought Aegia and their PhysX engine in February this year, allowing NVIDIA to integrate PhysX into its CUDA framework.

In the past, a PhysX PPU from Ageia was required to provide hardware acceleration for PhysX, offloading physics calculations from a system's CPU, allowing the CPU to be free physics processing and thus increasing frame rates.

By enabling PhysX on a supporting GeForce GPU, we get an increase in scores in Futuremark's 3DMark Vantage which includes a physics test. By offloading the physics calculation to a GPU, which is many, many times much more powerful, benchmark scores can sky-rocket because the rendering is no longer limited by a 'comparatively much slower' CPU.

Enabling GeForce-based PhysX makes the GeForce card taking over physics calculations instead of having the CPU to do the job. The result is a staggering three-fold increase in CPU scores.

This is a demostration of how much computing power a GPU has in it, but unfortunately, you do not stand to gain anything if the game does not support PhysX.