Why does the laptop slow down so much when the percentage is not used to the fullest?

Question

Iron

Lenovo laptop.
2.6 GHz, 8 GB of RAM.
After a month of use (and, of course, installing a bunch of programs), it began to slow down terribly.
This is seen in programs that require a lot of memory.
For example, Adobe Reader has become terribly slow to scroll documents, even small ones.
Up to a point everything was fine.
I'm trying to watch the performance tab.
I see that the processor speed does not even reach half.
It mostly hangs at 0.78 GHz, although the maximum speed is 2.6 GHz.
At the time of launching heavy programs, it reaches 2 GHz, then again drops to 0.78 GHz, but the application itself slows down.
How can you monitor what is wrong?
I am attaching screenshots of the CPU and Memory.
The jump is visible on the CPU graph - this is the moment the heavy program starts.

Answer 1

open the laptop, remove the ventilation, as a rule it clogs not from the outside but from the inside, clean it and you will be happy.
Externally, from the outside, the radiator looks like a completely clean one. you just need to remove it and clean it, as you see on YouTube.
sure 100%

Answer 2

Look at the railway, I also have brakes, but it is because of the disk

Answer 3

What about disk read speed? Mb it is fragmented? And the registry (it also needs to be cleaned periodically)? I would dig first of all in this direction.
Next - check for viruses, check performance in safe mode. Go through the services and processes, disable unnecessary ones.
If you know the approximate date, you can perform a system restore from one of the restore points, or delete what was set after this point.

Answer 4

Thank you all for your replies, I'll try everything.
In general, the very fact that the processor is not loaded even by half is confusing, but there are still lags in speed.
How can this be explained? I naively thought that the freezes should be due to the fact that the resources of the CPU or memory have been exhausted, but this is not the case here.

Answer 5

Disabling DMA could be, in theory. Or a drop in the performance of the disk subsystem for other reasons. I would suggest looking at the performance of individual pieces of the system: CPU, HDD, RAM

Answer 6

boot from LiveCD and test the hardware

Answer 7

download trottlestop run under admin, turn all parameters to maximum
multiplier and voltage to maximum,
power saving off
disable turbo off

Answer 8

hdd look at the broken ones, test everything in general. Well, look at the condition of the thermocouples.