Hey i just bought a hd 6970 graphics card and i've seen a few threads mention people running nvidia cards along side ati cards to use them for dedicated PhysX? Firstly does this achieve much? Is it worth the hassle? Also would my old 8600gts be able to handle this kind of thing? or would i need something newer to run PhysX?
it depends on you if you feel it's going to worth it or not. there are very few games out there needs dedicated physx card. they need the extra processing power from the dedicated card to enable extra physics effect (mostly for 'eye-candy' purpose since those physics effect does not have any effect to how you're going to play the games). however those extra eye-candy only for people that using nvidia cards exclusively. nvidia driver will automatically lock physx in the game if the driver detect other graphic card were used together with nvidia card though there are hack out there to re-enable the advance physx option in the game.
so as for your old card, it should be able to run physx though i do not know how much performance you're going to get from it
It's not worth the hassle imho - if you don't have an Nvidia card just leave it be. I doubt you would get reasonable performance from an 8600gts for physics, but even if you could, the driver issues, as described by renz, are a royal pain. Give it a go if you wish, but it's not something that I'd view as worth-while (although PhysX does provide some nice eye-candy).