Did a little experiment today;

Bios temps detected 40~48c ( randomly regardless of the weather/ambient temps )

Coretemp is almost always 9~11c lower than bios temps.
Realtemp is always 5c lower than coretemp reading.

Placed 70c on bios thermal shutdown, increased voltage from 1.335 to 1.515 ( to ensure that my processor hits 70c )

Coretemp at 69c = system shutdown ( take note the 9~11c offset from the bios temps )
Realtemp = 64c ( last seen before shutdown )

This is not to prove that realtemp is inaccurate but does this mean that the bios reading temps is similar to CT/RT when it comes to reading out idle temp ? ( needs calibration on idle but spot on when loaded )