I've posted this in another thread also:

E6600 @ 4.3Ghz, 2X 7900GTX @ 850/1070
FSB 1333 + RAM @ 597 3-4-3-4 vs FSB1066 + RAM @ 477 3-4-3-4 (RAM clocks reported by CPU-Z)




If what i've said before applies and the RAM is actually running at the same clocks in both cases, there's still something else involved since LH gets a consistent boost with FSB1066. On a side note, i needed higher voltages on MCH/RAM to run at FSB1066 setting.