The NB voltages are not reported in bios, i just toy with FSB/(G)MCH and Vcore....on the memory i just up the DDR2 voltage to 2.1V (+0.3V in bios), PCI-E and other voltages set to normal or Auto.

Memory timings, manually input 5-5-5-15 with all subtimings set to Auto, then you've got FSB/DRAM ratio...i set 2.50A which gives me 1063MHz memory speed.

FSB set to 425x8=3.4GHz, setting voltages to Auto in bios and starting to overclock will push the voltages way up, much more then you'll probably need.

The only way to find your limits and what is the least amount to voltage needed to gain a certain overclock is trial and error...might take you days to find the right voltage settings for your particular hardware.