Glossary:PhysX
PhysX is a video/performance option that is becoming increasingly available in PC games. It is a special form of physics processing, aiming the make more realistic particle and physics effects available in games. The company responsible for Physx was purchased by Nvidia in 2008, and since then has been featured prominently in Nvidia sponsored games.
Hardware
Originally, Physx acceleration required the use of a special PPU card, but these have been depreciated and are no longer made. Since the purchase by Nvidia, Physx calculations can be performed by CUDA-ready GeForce graphics cards (series 8 and newer, with a minimum of 32 cores and 256MB of video memory[1]. AMD cards cannot be used to perform Physx calculations, but some games allow use of the CPU to perform these calculations. The CPU code is less optimized and less streamlined then the same code for Nvidia based cards, meaning that users without an NVidia card will see performance hits with Physx enabled.
Nvidia limits Physx calculations to the CPU if the primary GPU is an AMD chip, even if there is a secondary Nvidia GPU installed. There are ways to Enable PhysX With Primary Radeon GPU.
Games Require Older Driver
See Ageia PhysX (Driver). This method is only recommended if your game is known to need the Ageia version of Physx.
Obtaining Latest Version
Nvidia GPU drivers usually feature the latest Physx drivers that are available at the time of release, but the latest Physx drivers can be downloaded here.