That's the whole problem? One particular motherboard will read 10 or more C lower than another particular motherboard. Factor in case temps and you can see a wide variance in temps even though both chips are likely similiar in "rise over ambient".
A reference without Motherboard type, Ambient case temp, and Socket-thermistor location is useless and ADDS to confusion. That's why we see all the "why is my cpu temp too hot" threads. Because they are comparing their own temps to people with motherboards that "read lower" than theres. And yes, some boards read significantly lower than others. A bi-product of AMD not forcing motherboards to read the XPs internal diode.
Mike