Hi Nitrogenarc,
I am using with sucess an NVIDIA 8600 GT XXX 256 MB for PhysX with my GPU ATI 4870 1GB. And a have tested with 9600 GSO for PhysX too with sucess on the 4870 at same machine. I readed that 8600 GT with 32 shaders is minimal hardware requeriment for good PhysX performance on a second dedicated card.
My SO is Windows XP SP3. My Monitor is an LG W2252TQ with two inputs, one DVI and other D-SUB.
My ATI Driver is 9.3 and NVIDIA Last Version driver with last version PhysX software.
Install Both Cards on Motherboard With Dedicated PCIEx 16X@16X Speed for GPU, and PCIEx 16X@4X Speed or better for NVIDIA PhysX Card. In my case 16x@4X Speed was enough.
Connect DVI Monitor Cable to ATI GPU and D-SUB Analog Cable to the NVIDIA Card. Two cables from same LCD Monitor, it have 2 inputs, it can be done with 2 monitors too, but with one is functional and more simple if it is possible. This are necessary because second card need the conection because SO need to detect if Extended Desktop is work property on Windows.
Clear Drivers windows with DC Drive Cleaner Pro, Install First NVIDIA Driver and Reboot.
Put Monitor into D-SUB Input (Analog). Windows Starts here because only NVIDIA driver is loading.
Now Install ATI Driver, reboot. Againg keep on Analog input, Because NVIDIA still principal monitor.
In this point we have 2 Drivers instaled with sucess and NVIDIA selected as Principal and loaded. Lets enable Windows Extended Desktop on ATI Card First, and after that change ATI Card to be the Principal Monitor.
Have Done, try fluidMark to test PhysX Hardware operation.
I am Playing the UT3 MOD for PhysX with 32 FPS Average and 27 FPS Minimum in both three PhysX levels. Comparing with PhysX by software i make 7 FPS at minimum, and 15 at Averange. I postage my poor results here. UT3 was really nice playable with 32/33 FPS... Its worth an second 8600 GT for PhysX with and first ATI 4870 card for rendering. 4850 arent so diferent i believe.
Mirror Edge is working really good too, but its diferent to analyse FPS, i have doubt about PhysX Software on my Intel Core 2 Duo E7400 is good enough too for compare its performance to the PhysX Card. Both are good. I think in my hardware Mirror Edge PhysX is less heavy in the training level (were i have tested FPS to compare PhysX Software VS PhysX Hardware). My FPS is Around 50/40 FPS with PhysX Enabled, at least 30 FPS.
I espected to have helped you anyway.
Seasky