High loading kpu with an adapter?

Question

Computers

I decided to lay the wires in the case, I bought a couple of extension cords, an extension cord to power the processor 8pin (4 + 4)
Without an adapter at rest 0-20% load, with an adapter 80-100%
Problem in the adapter (lack of power) or am I stupid?
I wanted to lay the cable, as the kpu cable barely reaches. (it hurts the design is tight for me).