Nvidia demonstrated the difference its PhysX capability can make for making a game look much more realistic and impressive. Using the free-to-play game Hawken, a recent blog post demoed the differences quite well. The game uses the Unreal Engine 3 and takes advantage of Nvidia’s physics accelerator incorporated in the GeForce cards.
A peer to the dedicated graphics card was marketed to the enthusiast crowd, the Physics Processing Unit. The PPU was developed by Ageia, a semiconductor company that developed a physics simulation engine and then developed it into a dedicated card that could perform the calculations much faster than the CPU. Ageia was the first to announce offloading calculations of video game physics from the CPU to a dedicated chip though video card companies Nvidia and ATI Technologies followed shortly after. Ageia was later acquired by Nvidia and the PhysX hardware acceleration was enabled on GeForce graphics cards.
This video demonstrates the visual difference side-by-side:
For more details on the difference you can see in Hawken, visit GeForce.com for the full article.