Ill try to explain but some of it might be wrong, Ive not studied electronics!
That part of the board is where the 3.3, 5 or 12v? rails get stepped down to what your Vcore is set to. Its done using the switching method - DC power can not be stepped down, so instead its switched on and off very quickly to simulate AC. The main components are a PWM controler to do the high frequency switching, MOSFETs, capacitors, donut shaped inductors...
The MOSFETs do the power conversion, and becuase of the type of chip they are, they only consume power (heat) when they change state. The frequency of switching is very high, 400khz if i remember, which means the MOSFETs are busy, and make lots of heat.
The capacitors are there to smooth out any ripple in the outut voltage and make almost no heat.
MOSFETs can only switch as fast as there rated for and when they get hot there ability to switch is reduced so the output is less stable.
My nf7-s has a cut up heatsink on the mosfets, which is passive and helps a lot. At 1.95v it used to varie between 1.75 and 1.9v!! since I added the heatsink I can go al the way up to 2.10v with 2.03-6 showing in mbm5. The cpu is more stable at higher overclocks.
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