im thinking about using a graphics card as a phisics card. and i dunno which 1 i will benefit from more . heres what im thinkin of building for my next pc
phenom II x4 920
asus m4n82 tri SLi DDR2 (4 Gb)
MSI NF980a tri SLI ddr3 (4 Gb)
2 x asus gts 250 (dual SLI)
1 physx card (asus gt 220 or gt 240)
im looking at those 2 cards because they are single slot cards and i want to be able to use the pcie x 1 slot next to the 3rd pcie x 16 graphics slot
for other useful pcie x 1 cards in the future
(eg. usb 3.0 card or 6gb sata card or a combo card [usb3 + 6gb sata)
unless i can buy a cable that could slot into the pcie x 1 slot and plug into a pcie x 1 card and locate it in another area of the case
"The good news here is that a GeForce GT 220 can be had for as little as $65 online, and as a dedicated PhysX card, it will guarantee that the High PhysX setting won't bottleneck performance. Even at 1920x1200, the GT 220 produced a minimum frame rate of 36 FPS as a dedicated PhysX card. Using more expensive solutions as dedicated PhysX processors didn't produce appreciably higher frame rates, so the GeForce GT 220 is a real PhysX champion for the price."
If you're already using nvidia cards for your main graphics, it's likely that adding a dedicated PhysX card will do exactly dick.
Here's a thread full of people on the Nvidia forums who tried that, and the conclusion is that in the majority of cases, you get no performance gain and the primary difference is that you use more power and generate more heat:
Basically, if your main cards are anywhere near decent, that can handle PhysX on their own more efficiently than if you involve a second card. If the second card is inferior, you can even slow down the whole process.
Not to mention, if you are using three cards, most motherboards will downgrade the last two slots from x16 to x8 or x4. That probably won't matter with a pair of 250s, but you certainly aren't doing yourself any favors.
Basically, dedicated PhysX cards are for if you have an ATI card as your main graphics card.