Technical article
NVIDIA JUST HAD one of their most sleazy marketing tactics exposed, that PhysX is faster on a GPU than a CPU. As David Kanter at Real World Tech proves, the only reason that PhysX is faster on a GPU is because Nvidia purposely hobbles it on the CPU. If they didn't, PhysX would run faster on a modern CPU.
The article itself can be found here, and be forewarned, it is highly technical. In it, Kanter watched the execution of two PhysX enabled programs, a game/tech demo called Cryostasis, and an Nvidia program called PhysX Soft Body Demo. Both use PhysX, and are heavily promoted by Nvidia to 'prove' how much better their GPUs are.
The rationale behind using PhysX in this way is that Nvidia artificially blocks any other GPU from using PhysX, going so far as to disable the functionality on their own GPUs if an ATI GPU is simply present in the system but completely unused. The only way to compare is to use PhysX on the CPU, and compare it to the Nvidia GPU version.
If you can imagine the coincidence, it runs really well on Nvidia cards, but chokes if there is an ATI card in the system. Frame rates tend to go from more than 50 to the single digits even when you have an overclocked i7 and an ATI HD5970. Since this setup is vastly faster than an i7 and a GTX480 in almost every objective test, you might suspect foul play if the inclusion of PhysX drops performance by an order of magnitude. As Real World Tech proved, those suspicions would be absolutely correct.
How do they do it? It is easy, a combination of optimization for the GPU and de-optimization for the CPU. Nvidia has long claimed a 2-4x advantage for GPU physics, using their own PhysX APIs, over anything a CPU can do, no matter what it is or how many there are. And they can back it up with hard benchmarks, but only ones where the Nvidia API is used. For the sake of argument, lets assume that the PhysX implementations are indeed 4x faster on an Nvidia GPU than on the fastest quad core Intel iSomethingMeaningless.
