Why would you put the voltage to go over the 600MHz signal? That won't help you much unless the FSB speed is also increased. So say you got the signal to 610MHz for an effective 1240MHz DDR signal. You will make it harder for the RMC and the RAC to build an accurate ratio between the FSB and the memory bus.
Under a 610MHz signal the FSB will have to be 152.5 to be at a 1:1 ratio. Say you got it up to 615MHz, that would need a FSB of 153.75MHz.
It will just probably make someone go nuts and will not be worth your while.
Back to you...
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