CPU Usage

[Travis King]

Why does my CPU Usage show 100%, but nothing other than
the items in my taskbar are running? I have another
program called CPUIdle, that is supposed to keep my CPU
cooler by disabling the processor when it is in idle. It
says that my processor's idle is 99%. So, I have the
task manager saying the usage is 100% (or the idle is 0%)
and I have CpuIdle saying that the idle is 99% (or 1%
usage) Does the task manager not work right or is there
a conflict?

 

[David Jones]

TLet me put it this way:

You have a program that "turns off" the processor when it
is idle (simplification but good enough).

If it does its job, the processor will never be truly
idle, because the program turns it off when it otherwise
would be idle.

Since the processor is never truly idle, Task Manager
never sees it idle, and as such your CPU usage is 100%.

 

[Bill James]

This is because of the way Windows XP calculates processor usage. Basically, it starts with 100% then subtracts idle time to determine the percentage of processor in use. Because CPUIdle causes the CPU to halt instead of idle it screws up the calculation (if there is zero idle time then usage always shows 100%).

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Bill James
Microsoft MVP·DTS

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