Actually, this is true. Different mobo's may implement the standards differently. You'd be amazed ....
For example, I just got my PIII-S. It's supposed to run at 1.45V. However, when set to default voltages, my mobo, according to the BIOS and sandra, only supplies 1.42V. When I manually set it to 1.45V, it gives it 1.48V, and when I try 1.425V, it gives it 1.7V. (All reported voltages.) When I set it to 1.4V, it gives it 1.42V, just as in the default configuration. Since the board is 100% stable, I'm guessing that it's a combination of the board supplying too little voltage and the sensors under-reporting those voltages. This is all on a Shuttle AE25.
Now, I got the CPU from deez, and on his board (Asus TUSLC2, if I remember correctly), it always reported as 1.45V. So there's an identical CPU on two boards with the same chipset, showing different voltages ....
Strange, eh?
-- Paul