My laptop is over 3 years old, I use it for a lot of heavy tasks and gaming and runs for long duration almost everyday. It has been perfectly fine for so long and meeting all my computing needs, until today, when I tried to play games as usual I realise my CPU is throttling, CPU speed drops to 0.4 GHz (duration can last from few seconds to a minute or longer, inconsistently going up and down) and causing massive FPS lag in game. I have never cleaned the fan and repaste throughout the years, and so I went to do some research and thought overheating might be the cause. So, I went to service center to clean and oil the fan, make sure it is runnning properly (NOT broken) and apply new thermal paste (old paste has well dried up). I tested my laptop on the spot, ran some games for 5 mins just to do a quick stress test, make sure CPU does not get throttled and everything seemed fine. Few hours later when I back home and try to play games, CPU is throttling again, see below.
I think it's not overheating (FYI, the temperature was jumping between ~50C to ~70C, did not really hit over 80C). I do not entirely rely on laptop fan when I game, I additionally use heat absorber (a small device like a vacuum that sucks out the heat from the ventilation) to help with the cooling, not as powerful as you may imagine, but does help at a minimal. And also, I am undervolting my CPU, limiting both CPU core and CPU cache offset voltage at -100mV. I don't understand why is my CPU still throttling? For over 3 years this has NEVER happened until today. I did my best to solve this before I decide to drop a question here, send help...
EDIT 1: POSSIBLE CAUSE (NOT OVERHEATING)
Okay, after I spent some time to monitor and test around, I decided to rename the title as I am pretty sure the CPU throttling is not caused by overheating. I notice my CPU speed is fluctuating between 2 GHz to 3 GHz and higher when utilization is low and laptop is not running heavy tasks (games, for example), just browser, Discord and Spotify. See screenshot below. (if I play games, CPU goes throttling inconsistently just like what I explained above before edit 1.)
I think it has not always been this way, otherwise my CPU would have throttled a long time ago, only these few days when I'm trying to tweak around (explore overclocking & undervolting) using XTU and ThrottleStop. I swear to god, I did not modify ANYTHING using XTU, I tried to tweak the clock speed or whatever with XTU but it does not support my specs I can't modify anything at all, so I switched to ThrottleStop to do undervolting in hope of fix. Okay, as I said, I guess it has not always been like this (CPU speed fluctuating) but I am not sure why is my CPU running abnormally, is this unusual for CPU to act like this? What is the cause?
A temporary fix is to disable turbo in ThrottleStop, the CPU speed then locks at 1.58 GHz (for my CPU) and no more throttling. This is the result when I disabled turbo and play games:
SO WHY? Why is my CPU randomly turbo-ing all the time and throttled when I play games?
