From Wikipedia.
On anti-competitive practices:
Versions 186 and newer of the ForceWare drivers disable PhysX hardware acceleration when a GPU from a different manufacturer, such as AMD, is present in the system.[14] Representatives at Nvidia stated to customers that the decision was made due to development expenses, and for quality assurance and business reasons.[11][15] This decision has caused a backlash from the community that led to the creation of a community patch for Windows 7, circumventing the GPU check in Nvidia's updated drivers. Nvidia also implemented a time bomb in versions 196 and 197 which slowed down hardware-accelerated PhysX and reversed the gravity, leading to unwanted physical effects[16] - which was again remedied by the updated version of the community patch.[17]
On 5 July 2010, Real World Technologies published an analysis[21] of the PhysX architecture. According to this analysis, most of the code used in PhysX applications is based on x87 instructions without any multi-threading optimization. This could cause significant performance drops when running PhysX code on the CPU. The article suggests that a PhysX rewrite using SSE instructions may substantially lessen the performance discrepancy between CPU PhysX and GPU PhysX.
In response to the Real World Technologies analysis, Mike Skolones, product manager of PhysX, said[22] that SSE support has been left behind because most games are developed for consoles first and then ported to the PC. As a result, modern computers run these games faster and better than the consoles even with little or no optimization. Senior PR manager of Nvidia, Bryan Del Rizzo, explained that multi-threading is already available with CPU PhysX 2.x and that it is up to the developer to make use of it. Automatic multi-threading and SSE will be introduced with version 3 of the PhysX SDK.[23]
It's hard to make sense of Mike Skolones' comment that "modern computers run these games faster and better than the consoles" because "most games are developed for consoles first and then ported to the PC".
Some forms of physics modelling are suitable for parallelisation and some are not. I don't recall Havok based games running into CPU bottlenecks. In fact CPU-limited games are rarer than hen's teeth.
This conversation badly needs to get away from the nVidia vs AMD thing. When Apple were underdogs they complained bitterly about Microsoft's dirty tricks. Now they're on top, they're as bad as Microsoft ever were. Microsoft haven't gotten much better either. Back when Netscape was on top in internet applications, it wrestled with all it's might for power over consumers; it only started complaining when it lost out to Microsoft. Such practices are nearly universal among companies that have the power to carry them out.
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