Can anyone shed light on some things from this recent testing of Radeon 7950?
We've transitioned our test platform for graphics to a Sandy Bridge-E-based Core i7-3960X overclocked to 4.2 GHz. You'll notice that, in some cases, that's still not enough processing power to let some of our more demanding two- and four-GPU configurations really stretch their legs.
When you start getting into multiple high end GPU situations in some games you will get CPU bottlenecked, even with a top Extreme Edition processor. The problem comes from the fact that no game uses more than 4 threads. So the i7 extreme's 6 cores plus hyperthreading are not fully utilized. If you put a quad GPU setup at a lower resolution with any CPU, even top of the line, the CPU will be the first thing to run out of steam, simply because there is so much GPU horsepower in play. That doesn't mean that you won't get good framerates under those conditions, it just means that your GPUs will not be working at full power unless you increase the resolution dramatically, shifting the workload more towards the graphics cards.