This is from GTJ's Bad Axe 2 guide. Hope it helps.

"The aSC7621 hardware monitoring chip also monitors 5 voltages: the standard 12v, 5v, and 3.3v supplies that do the bulk of the non-cpu work, and VCORE and VMCH (sometimes labelled simply 1.5v). The monitor is fairly accurate and will probably show the VCORE and VMCH slightly lower that set via BIOS. This is a normal artifact of digitally controlled voltage regulators. While VMCH should remain constant, the VCORE will probably change in response to power saving features like C1E and EIST. The VCORE can also change due to a phenomenon known as Vdroop. This is basically a "brownout" situation where the VRD can't supply the required voltage under extreme load. A certain amount of Vdroop is normal and, although I can't verify this, it's said that the XBX2 has one of the lowest Vdroops around.

There does not seem to be a way to monitor the memory voltage other than with a multimeter. You can do so by probing here: Memory Voltage measuring point. You can also measure VCORE and VMCH: CPU Core Voltage measuring point and MCH Core Voltage measuring point. Measure safely please. The voltages themselves aren't dangerous but an X6800 processor, for instance, can draw 90 amps. Short that to ground and the least of your problems will be getting a new board."

http://www.peakin.com/xbx2/index.html