What is the System Idle Process and why is it using 96 to 99% of the CPU?

This is a great example of things we geeks probably take for granted, that's not always obvious to the rest of the world.

I mean, really, a process that regularly takes up 99% of your CPU's time must be a bad thing, right?

Nope, not at all. Just the opposite, in this case.

First, let me show you what we're talking about.

Firing up Windows Task Manager, and then clicking on the "CPU" column to sort by CPU Usage, (click again to reverse the sort order if all you see are zeros in that column) you'll often see something like this:

"Think of it as your computer just twiddling its virtual thumbs, waiting for something more important to do."

You can see that something called "System Idle Process" is taking up a full 92% of my CPU's resources.

Seems like a lot, so what's up with that?

The fact is that most computers can never really do nothing. When the computer is on, the CPU's running and it must do something - even if that "something" is waiting for something real to do.

Think of it as your computer just twiddling its virtual thumbs, waiting for something more important to do. The computer's doing something (virtual thumb twiddling), but we wouldn't call that doing anything useful.

That's called being idle.

And the "System Idle Process" is the software that runs when the computer has absolutely nothing better to do.

It effectively runs at the lowest possible priority so that if anything, anything at all, comes along for the CPU to work on, it can. When there's nothing left to do, back to idle it goes.

So having the System Idle Process using 90% of your CPU is a good thing ... it means that that 90% is readily availble should there be any real work to do.