maybe not Physx, but something similar.
hint : http://www.behardware.com/articles/770-9/report-amd-radeon-hd-5870-and-5850.html
Compute shaders
The final significant innovation introduced by Direct3D 11 is known as the compute shader or DirectCompute. [...]. Compute shaders have the advantage of being standardised and therefore directly supported on all compatible graphics cards[...]. The other advantage, mainly in version 5.0, is that they have been designed to interact efficiently with a 3D scene in DirectX, which simplifies usage for physics calculation or non-polygon geometry or even post processing effects [...]
To facilitate their introduction Microsoft hasn’t only added compute shaders at 5.0 but also 4.0 and 4.1, so as to give support on DirectX 10 and 10.1 generation graphics cards, with a few limitations of course.
more at the end of the page of the link.