i5 5200u jumping from 2.5ghz to 0.8 and back

well, I need to fix a laptop cause its slow
one of the problems I found on it, was that the cpu was going extremely slow
and saw it was stuck on 0.8ghz, I went to find something about it and found that putting high performance mode will help and I did and now it goes from 1.2ghz to sometimes 2.7ghz which is the max turbo mode. 2.2ghz is the base clock which it jumps around. the voltage is also not normal, it goes from 0.89 to 1.018 which is a huge change (have tried overclocking my own i7-8700k and found out how huge a 0.05 change is)
is there a way to set a voltage which will not change?
i want to keep the laptop at 2.2ghz no more than that.
 
Solution
EIST = Enhanced Intel SpeedStep Technology. Look for something like Intel Speed Step or similar.




base clock will jump around. Its a FEATURE that makes sure CPU will save as much heat and battery power as it can. its 100% normal. my cpu can go all from 0.78 Ghz to 3.7 GHz.
if you lock it on top speed you will loose both SPEED AND BATTERY time. If cpu will waste time in full speed, it will use battery and make only HEAT. When you will want it to turbo, it will be stoped by that HEAT.
what you can do is move that moment WHEN it goes down. but don't block it or you will have it even slower....

what you need is all here:
https://www.glarysoft.com/
get free version, run defrag, cleanups etc.... DONT TOUCH CPU.
 
 

where do I do those? I know turbo mode is in the bios but haven't found a way to actually enter the bios on this laptop