FUD Zilla tested the new FluidMark PhysX benchmark from Ozone3D and found out that PhysX on the GPU task the CPU a lot more than PhysX on a dedicated physics processing card:
However, we wanted to test to see if there was any difference in performance depending on CPU usage, so we also did some tests running CPU Burn-in which loads the CPU and as we’re using a dual core CPU we ran two instances of CPU Burn-in to load both cores to 100 percent.
The results are intriguing to say the least. With no extra load on the CPU, the Ageia PPU scores 1,753 points, or an average of 30fps, while the Geforce 8800 GT card manages 4,921 points or an average of 83fps. A clear lead for the Geforce card, but things are set to get interesting.
When we loaded the CPU to 100 percent things changed dramatically for one of the cards, and it’s not the Ageia card. Even though the PPU took a performance hit down to 1,282 points or 22fps, it was nothing compared to the performance hit that the Geforce card took, as it dropped all the way down to 1,344 points or 22fps.
It seems like the Geforce PhysX implementation is highly CPU dependant and although some of this might have to do with the CUDA implementation, we didn’t expect to see the kind of performance drop we saw. It doesn’t bode well for PhysX in CPU heavy games and as yet we have no idea how well it works in GPU heavy games.