For Windows Task Manager, why does CPU and Memory usage constantly fluctuate ?

I noticed that despite running the same programs and apps, the CPU and memory (according to Windows Task Manager) constantly fluctuate. At one moment, CPU and Memory usage might be 99% and 75% respectively. And the next moment, it drops down to 35% and 25% respectively. All this happens despite the fact that I'm running the exact same programs and apps the whole time, so there shouldn't be any major fluctuations in CPU and Memory usage. I'm using the same amount of system resources yet WTM says otherwise.

Why does this happen? Wilderssecurity's help is greatly appreciated.

 

when idle your CPU should be below 5%.

if the lowest your CPU goes is 35% you have way too much stuff running.

 

Not in my case. With only Firefox (8 tabs) and Thunderbird running, the CPU usage doesn´t go below 35%. The culprit is Flash (11.7.700.202).

 

Processes come and go, and the resource usage changes.

There are hundreds of factors that can affect it, including background stuff.
You then have scheduled tasks, updates, etc, all of which make a difference.

A properly configured system at idle will consume ~0-1% cpu.

Mrk

 

I also think it depends on your system specs.
In my laptop (Which has lame specs) it usually idles at around 10% with almost nothing installed. (Browser, Office suite, PDF Reader and a couple things that do not run in the background)
With my Desktop i have tons of things installed and running in the background but it never idles above 5%.

Still, i think 35% is way too high. As Mrkvonic said, it could be so many things.

 

If you use a Task Manager or SysInternals Process Explorer type tool that shows CPU usage for each process (history chart displays are particularly useful), you can zero in on what is consuming CPU time. For even more detail you could use SysInternals Process Monitor to look at various types of operations.

 

Could be a lot of things really.. if you're running Win 7, it could be defrag running in the background at various times, it could be your AV or security suite scanning in the background at times, if you're watching flash videos, flash is notorious for hogging cpu and it can fluctuate way up and down. Obviously something is going on that you're unaware of. But as some have mentioned, after the computer has settled down and sat idle for quite a while, cpu usage should be near zero when you're just sitting idle doing nothing.

 

Having "8 firefox tabs and flash" open doesn't exactly equal an "idle PC" as is being discussed.

 

Actually, these results change a lot. I checked today with the same 8 tabs and Flash, and the results are different. Now the "average" CPU usage is very low. The computer is "almost" idle.