Not all that accurate really. Voltage level readings in a computer are more an afterthought than anything realistic anyways. They are there to so you when something is happening like a bad overclock that is pushing a componant to far more than anything else as far as we the user are concerned. If the voltages go to far out of whack a computer won't even start. That said though a Bios can affect the readings in so far as it's multiplier settings are concerned with how it sets up to interpret the data from the sensor info on the MB. However like I said for a true reading the only real accurate indication is with a meter.