Question Cpu usage dropping

[wojakkk]

When im playing some games , my cpu is like:
60 fps / 90% usage
but sometimes goes to:
32 fps /20% usage
thats causing lag spikes.

Anyone can help?
Thanks for all the help

 

[rgd1101]

and the gpu usage?
what the cpu/gpu temp?
make and model of the psu?
full system spec?