What is the System Idle Process and why is it using most of the CPU?

The devil finds work for idle processes. :-)

And so does BOINC.

http://boinc.berkeley.edu/projects.php is a list of projects you can donate idle cycles to when you install the BOINC software. It can either run in the background as a low-priority process, eating up idle cycles, but giving up cycles when your priority programs need them, or as a screensaver, using more of your CPU when the whole system is idle.

The projects range from evaluating radio signals from space for signs of E.T. communication to helping with complex mathematical modeling. It's a great way to take those idle cycles away from the System Idle Process and donate them to worthwhile projects, making your computer a voluntary node in a giant distributed supercomputer.

Apparently, what the System Idle Process is actully doing is continually issuing HLT commands to the CPU; HLT being a command which, according to http://download.intel.com/design/PentiumII/manuals/24319102.PDF, "stops instruction execution and places the processor in a HALT state ... An enabled interrupt, NMI, or a reset will resume execution".

Apparently doing this saves power, which raises the question of what the CPU would be doing that would use power if the OS *didn't* continually issue these HLT commands. Any ideas?

I am using WIN Vista Home Premium. I ran Task Manager, went to Processes, sorted the list and could not find the System Idle Process. Whats up with that?

Thanks

On Vista machine you'll also find that "SearchIndexer.exe" may be chewing up lots of CPU time from time to time. Vista will only show the current user's processes initially - if the user is logged in as an administrator, they can click on the Show All Processes button on the bottom of the dialog box to see everything running on the system.

Hi
The Idle Process can kick in when you are engaged in when you are using Movie Making software and are downloading or writing video causing you to lose or get distorted clips or frames. To get around this you can deliberately start the Idle Process so that it effectively gets it out of the way and won't start up in the middle of your movie making. You can also use a little program called "End It All" which also helps, but thats a different thread.
David

Simon said: "which raises the question of what the CPU would be doing that would use power if the OS *didn't* continually issue these HLT commands."

Adding 0 to 0. Repeatedly. :)

Actually, that's a joke. What it would do is check over and over again if anything's happening, like a key being pressed or the like. Read http://en.wikipedia.org/wiki/Busy_waiting (and http://en.wikipedia.org/wiki/HLT while you're at it).

Also, thanks for pushing me to research this :)

Sometimes my machine is running idle and it cannot be interrupted. That is, the idle process is too busy to notice keystrokes and mouse clicks.

Leo, do you know why this is happening?

I once read something about WinXp automatically moving files about, a kind of optimisation. When I can't interrupt the idle process there is certainly a lot of disk processing (I can hear the heads thrashing). I haven't been able to find the information about automatic file positioning again and sometimes wondering if it was a figment of my imagination.

The point seems to be that users expectations are that the SIP should not take over the machine, but it does, interferring with the usefulness of the computer. There have been many times for me when a program has appeared to have crashed when in fact the computer is just busy doing the SIP. If the SIP is housekeeping processes and commands to keep the processor occupied during periods when programs are inactive then as soon as a program requires the CPU, the SIP should be suspended. So either the SIP has been badly programmed or it is more than the computer sorting itself out. Either way this is very frustrating to users and a way to control the SIP would be really welcome.

On my computer i found the same thing, but while transferring a massive 120 gb folder from partition to partition. Needless to say it is deadly slow, should,nt the processor consider that an opportunity to maximize the cpu to decrease time? Or did i miss something here, =)

Leo, I understand what you are saying about SIP not interfering by definition, or by design is probably better. But what Hawkins, Webb, and Milton are saying is true. In practice, I have often noticed momentary hangs in the application I'm working with when SIP kicks in (this is XP SP2). Whatever the intent, SIP does in fact interfere. What is needed, as Milton says, is user control of this feature.