Ok I just used a multimeter and tested them via the 20 pin, and it read as follows:
Full ~ No Load ~ Under Load (Tested with Prime95 'torture test')
3.3 ~ 3.31 ~ 3.3
5 ~ 5.01 ~ 5.01
12 ~ 11.97 ~ 11.96
Should I care about the 11.97/11.96 (being a new PSU)?
thanks for the advice, it's nice to know my Mobo sucks for reading the voltages
Hehe. So thank you both, Nubis and ImUseless!