iXBT Labs posted a review on the Intel Core 2 with Various FSB/Memory Clock Rates

In case of popular Core 2 processors with 1066/1333MHz FSB, it takes sense to use dual-channel memory of much higher bandwidth than the nominal FSB can provide. If we consider DDR2-667 the reference point, fast DDR2 or DDR3 memory can bring a 6-8% performance gain in real applications.

Intel Core 2 with Various FSB/Memory Clock Rates