What does CPU usage actually mean?

[Guest]

What does CPU usage actually mean?

I'm almost positive it doesn't have anything to do with the clock speed, as I haven't noticed any relations between the two.

Does it refer to the amount of instructions per cycle the CPU is doing?

Please explain.
Thanks!

 

[Hlsgsz]

CPU usage means how much of the CPU's total resources are being utilized at a given moment.
Modern CPUs decrease their frequancy when the are very lightly utilized to reduce power and heat and ramp up whenever a heavier task is sent their way.

 

[spdragoo]

It means how much of the CPU's resources are currently in use: 10% = 10% of the CPU is being used, so there's another 90% available for other apps; 75% = 75% is in use, so only 25% is available for other apps; 100% = your CPU's resources are completely tied up, with nothing left for any other apps (which have to either wait for the current app to finish or wait for the CPU to shoehorn them in the queue).

The only way you can actually compare CPU usage is when you are comparing identical systems: same CPU, same amount/speed of RAM, same speed/interface type for SSD/HDD/DVD, same Ethernet/Wi-Fi connection speed, etc.