Right. I've looked high and low on the internets, and I can't find an answer to this.
Many BIOSes for AM3 boards have the following options, to change their voltage settings.
CPU NB Voltage
There are other voltages, too, but these are the ones I'm concerned with.
Here's an actual screenshot, so you don't think I'm insane
Changing this value clearly has an effect - overclocking and increasing the CPU NB VID Control will increase stability.
AMD overdrive also shows this value.
See under voltage on the bottom right, you have both NB VID and NB Voltage.
Can anyone properly explain what this is, what it does, and how it all fits together, please?