Slowing Processor speeds when playing

So I've noticed that once I go into games that my processor actually slows down, and my performance tanks because of it
I usually run at 2.65 GHz (.5 GHz overclock), and when I enter any steam game, my processor stays at 2.65GHz, then goes down to 1.74GHz or 1.47GHz after 20 seconds or so
If I exit the game, my processor stays at 1.47 GHz
I used to be able to play at 2.65GHz, but one day it just stopped working
What's happening?

PC Specs-
HP Pavilion 15 Notebook PC
Windows 10
Bios- F.10
Processor- AMD A 10-5745 with Radeon(tm) HD Graphics (4CPU), ~2.1 GHz
Memory- 8192MB RAM
DirectX- 11.2
Graphics- AMD Radeon(TM) HD 8610G

Possible things that might affect it
Asus GPU Tweak
Bitdefender (though ive screwed with profiles, and I don't think "game" setting affects this)

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This is true.

To control heat production or rather destruction of a CPU (yes, yours has a APU) the speed pulls back as the temp goes up.

Since it worked before the usual causes are dust buildup (keep reading), some heatsink compound dried and cracked or other.

Tell me if you kept up with the 1st of the month canned air routine as well as did you place it on a laptop cooling pad.

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I actually have an AC under my laptop running at all times, keeping my laptop at a cool 24 C at all times, highest ive seen is 27
and it wasn't a progressive slow down, one day it was 2.7, the other 1.4
and yes I do clean dust regularly

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Then the news is grim.

Since cooling and cleaning didn't help it's time for some tech to replace heatsink compounds and hope.

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After further tinkering, I have found a few strange phenomena
first off, I changed asus gpu tweak with amd overdrive

I go into game, cpu now drops to .86, I alt tab out, and I return to 2.65 in a matter of seconds

I have booted game without overclock, still drops to .86

Also, my processor seems to be locked at 2.65 GHz now, I'm not particularly complaining, but strange nonetheless (like it wont go back to its original 2.1 GHz)

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