U guys are all completely ignoring the fact that all boards have vdroop.
:X
OP, theres a thing called vdroop.
What that means is your voltage will dip below what u have in bios.
The degree of Vdroop is dependant on your board quality.
The better he board the lower the vdroop.
Some boards now even have something called load line cailbration or Vdroop control.
This will ensure you get constant voltage during load and idle.
Without options like that... you will never get constant voltages for load and idle, because vdroop is a part in EVERY BOARD.