but why do you need a special physx driver? it should only require a cuda driver and the cuda driver should come with the graphics driver in my opinion. if there isn't a cuda driver then the physics engine automatically should use the cpu.

as far as i know the gpu still isn't used for gameplay physics anyway but only for eye candy stuff like particles and cloth.

it makes no technical sense. no other physics engine has such silly requirements.

physx is the main physics engine because they have loads of marketing money. not because it's better than others. they even have paid many aaa developers for using it.