Unlike real-world games, 3DMark requires a Physics benchmark run in order to provide a full score. That benchmark runs amazingly slow using the CPU as a physics processor and incredibly fast when using the GPU. Of course, the GPU Physics feature comes in the form of PhysX, which is a proprietary Nvidia technology. 3DMark awards the added "performance points" to the CPU score, since it’s using the GPU as a CPU.
During actual game play, enabling PhysX slows the system slightly, while disabling PhysX disables advanced-physics calculations. Trading a few frames per second (FPS) for increased realism is viable for games, but judging any performance difference between competing products requires that all products support the same setting. Adding proprietary calculations removes standardization, which is a benchmark that’s supposed to be a standardized test, so we chose the Disable PPU option in 3DMark to make this an apples-to-apples comparison.
3DMark and GPU test scores favor the GeForce GTX 285 over the GTX 280 by an average of 7 to 8% percent.
CPU scores are separated by less than half of one percent, which is an expected result when the Disable PPU setting prevents benchmark inflation.