https://forums.tomshardware.com/threads/gpu-staying-at-300mhz.3426440/
GPU SCLK: 300 MHz at idle is normal.
GPU PWR: should be lower, mine stays at 7-15W (Check your PSU and voltage) I have Corsair CV-650
When in-game the GPU SCLK should stay fixed at max value, I have the RX 570 4 GiGs which...