Wrong CPU Temperature Measurement?

[TerminalPro]

So recently found out something a little strange. I have been using "CoreTemp" to monitor my CPU temps, however a few moments ago I had to edit something in the BOIS and came across the CPU temperature monitor in there and it was displaying a different value, quite different to the CoreTemp one.

CoreTemp shows about 20-20 degrees at idle
BIOS shows about 30-35 degrees at idle.

Any idea what is going on here? All this time I've been listening to CoreTemp and thinking my PC is extremely well cooled. Now I don't know what to think :/

CPU is an AMD FX 6300

 

[TerminalPro]

Something I should add is that as soon as I log into my PC, CoreTemp opens and displays around about what the BIOS displayed, but then the value starts to reduce. Perhaps the BIOS is displaying the worst case scenario or something?

 

[mamasan2000]

If it's like the FX-8350 temp readings, temps under 40 C aren't measured, they are calculated and not accurate. Over 40 C is accurate. So trust BIOS.