It seems that today Hybrid ATI+NV PhysX systems (ATI GPU for graphics, Nvidia GPU for PhysX) are even more popular than Ageia PPUs in their time. Not officially supported (and chased) by Nvidia, such configurations are possible using custom patch.
This time, our colleagues from PCgamesHardware.de have published results of Hybrid PhysX tests in Batman: Arkham Asylum built-in benchmark.
To built a Hybrid PhysX System, you’ll need mobo with two PCI-E slots (regardless to SLI/Crossife support; PCI-Ex8/x4 is enough for PhysX), appropriate Nvidia GPU (something like 9600/GT240), Win XP/Win 7 OS and PhysX mod 1.02, which you can download here.
Installation instructions – Link#1 | Link#2 | Link#3 (Please note that most of them refer to old PhysX mod 1.01 – use 1.02 mod instead, download link above) | Link#4 | Link#5 (video guide) | Link#6 (Italian video guide) | Link#7 | Link#8 (detailed) <- it’s recommended to start from newer links.