Weird ghz issue

Nov 3, 2018
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I have been having this problem lately and its really bothering when ever my computer is running the cpu randomly drops to 1.36 ghz then goes back up to 4ghz then repeats it self its happens when i play games and when im just sitting on my homescreen doing nothing i upgraded my cpu to see if that would help but nothing happened it does the same damn thing, anyone have any idea what could be causing this?