Intel Q9450 vs Phenom 9850 - ATI HD3870 X2

[Boschwanza]

So in this case a 40% decrease in FSB BW translates into a 7-10% hit in FPS.

From my personal opinion C2Q has no problem with bandwidth itself and never had. The problem with the fsb is its latency. Increasing or decreasing FSB has just an effect in terms of bandwidth but latency stays always the same. You can easy check this with low level Benchmarks.

In other words FSB is not a big problem in terms of bandwidth but there is a physical way on the PCB the Data must go through. Wheter the Data has to go through PCB layers decide in comparision to K10 and Nehalem, whether the coherenc latency is μs or ns. This is a very significant factor, which allows K10 and Nehalem better scaling vs Core2Q.

So what an effect does this have in real life conditions. In a good case the prefetcher can offset this physical latency, the data is already in the L2 Cache and can be calculated (in fact in this case there is no latency) in a worse case the prefetcher works inefficient and the physical latency of the FSB results in poor performance. And exactly thats when K10 outperforms an Inte Core2Quad.
I excuse my bad english, if there are any question feel free to ask.