I've seen a few outragous claims about what is required for a dedicated PhysX card. So I decided to do a quick test with what I had laying around to see. The two biggest things I've seen are: A 128-bit makes the card too slow. A G92 w/ 112 shaders is needed. Ok, this is just a quick test, using Batman:AA, because it is the holiday weekend, and I didn't want to spend hours pulling machines apart and benchmarking every combination I could. Test setup: Xeon X3370@3.6GHz RAM: 8GB PC2-800 4-4-4-12 eVGA 780i Primary GPU: GTX470@800/1600/900(c/s/m) PhysX GPU: 9600GT PSU: Corsair HX850 Column 1 Column 2 Column 3 Column 4 0 Min FPS AVG FPS Max FPS 1 PhysX Disabled 74 128 186 2 CPU PhysX 11 17 26 3 GTX470 32 61 102 4 GTX470+9600GT 32 61 102 5 GTC470+9600GT UC * 27 58 102 Some interesting results. There was no change by adding the 9600GT, kind of odd, I expected better performance. So that by right there tells me the GTX470 is powerful enough to do PhysX in Batman itself. I'd try again with Metro, but I can't find an accurate way to benchmark it easily. To me this confirms also that when PhysX is enabled, at least with Batman, performance is purposefully limitted, probably to meet a target framerate to ensure smooth gameplay. Now, in the last test, I underclocked the 9600GT as low as possible, both the core, shaders, and memory. I did this to see how a much weaker card, with far less memory bandwidth would perform. There was almost no difference, but it did finally show a little performance difference. There are also other users that report great results with 128-bit cards. Erocker uses a GT240 with his HD5850s in crossfire and reports good results. Now, what is my conclusion? You don't need a powerful GPU for PhysX. PhysX relies more on the shader power of the GPU then the memory bandwidth. Remember, the original PPU only had a 128-bit bus. I think the minimum I would recommend for a dedicated PhysX card is a GT220, or 48 shaders. I would not recommend anyone with a decently powerful nVidia card already to waste any money on a dedicated PhysX card. Anything from the GTX200 or GTX400 series is enough, don't waste your money. For anyone with an ATi card wanting a dedicated PhysX card, do not spend a large amount of money, and don't worry about getting a high performance card, go by the minimum I set above. For the small number of games that would even use it, it isn't worth spending more then $50 on a card.