31118 GPU score on HD 5970.

Yeah I don't think it's really the CPU bottlenecking. You should try running the test on High instead of Performance, Performance doesn't use as much resolution or AA or AF so you'll stress the GPU harder with an H score.

That said, my crossfire 5850s can do P30k with an i5 750.
 

kokin

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It might be because when you OC your CPU, you're also OCing other parts as you raise that FSB.