gpu physx compatibility

The gpu physx compatibility tag covers work to run older GPU-accelerated PhysX effects on hardware outside their original NVIDIA support path. Current coverage centers on ZLUDA 6, an open-source project that adds early 32-bit GPU PhysX support for some older games on AMD Radeon graphics cards. The featured example is Mafia II, where ZLUDA is reported to deliver a substantial performance increase by handling the PhysX path on Radeon without requiring a second NVIDIA card. This tag is useful for following developments in graphics compatibility, legacy game support, Radeon hardware, and efforts to preserve older PhysX features across different GPU vendors.