In article ,
wrote:

Is this a common option in bios's ?

No. Common options are Vcore, Vagp, Vdimm. Only a hardware hack with a
resistor can modify the Northbridge voltage, and that was only necessary
for 1.04 rev boards. Currently shipping boards should do DDR400 on
the Northbridge, no problem. As far as I can remember, you can only
push it a little further than that, so DDR400 is a fine place to stop
and enjoy the performance.

Paul