graphic card: 5600xt
Tried a coupld updates since 20.10.1 and it seems everyone of them has this issue.
At first I noticed my GPU fan was keep turning on from time to time when I'm not running any games.
And today I finally found the problem.
all these update keep the VRAM clock running at full speed. even I'm not doing any tasks and only running 60hz monitor.
Fix: downgrade to 20.10.1.