PCIe Speed Test v0.1 CPU-GPU/GPU-CPU bandwidth test

[Lightman]

Wow...

Crossfire and X2 systems definitely manage system bandwidth much better than single chipset GPU systems. I still fail to understand how the CPU to GPU and GPU to CPU bandwidths aren't close to exactly the same on single GPU systems. My only guess is the GPU doesn't need to send as much information back to the CPU to function, so this speed is artificially limited. CF and X2 systems must need a lot of GPU to CPU bandwidth to coordinate their efforts. This is just a hypothesis/guess after seeing all these scores. Lets get an ATI chipset engineer to explain what we're seeing. Somebody on XS has to know one!

I've came to the same conclusion while thinking about it!
My guess is that as soon as multi-GPU is detected some routines in driver are enabled to handle increased bandwidth between CPU and GPU.

EDIT:
Some proof - this is what I get after simply disabling CF in CCC