For me there is a fair bit more bandwidth @ 475 x 8 & the latency is a bit lower too. Its not really the FSB thats making the difference its just that the RAM speed is a bit more optimal for higher CL5 running whilst still on warranted voltages.
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The vNB & vDIMM in my post above are just a touch higher up than they need to be to keep the rig stable its just I was playing with slightly tighter RAM timings before I done the Prime run & just left the voltages as they were.
Gonna have to try 475. hehe, seems we have the same mobo, cpu and ram (and psu?). It will be an interesting experiment seeing how my rig compares to yours at exact same settings.