Idle Process

[Durt 2]

I'm confused as to what the idle process does. I was under the assumption that the idle process issues a HLT (halt) instruction when the CPU was no longer needed by another process. Then the idle process fired up the CPU again when another process needed it. This made sense because my computer is considerably cooler when idle, compared to when under %100 load.

 

Then I read this tech note that sort of contradicted this. Here's a quote:

 

Quote:

The processor can never be sitting idle waiting to the next task, unlike our cashier. The CPU must always have something to do. It's like when you turn on the computer, the CPU is a piece of wire that electric current is always running through, thus it must always be doing something. NT give the CPU something to do when there is nothing else waiting in the queue. This is called the idle thread.

 

So could someone give me a deeper insight as to why my CPU is cooler when "idle" compared to not.

 

Another question, somewhat related. The game server for BF:42 (BattleField 1942) would jump to %100 percent when just one person joined in the game. When idle, the BF:42 server program only used 2-3%. They then patched game, and now the CPU usage jumps a negligable amount when someone joins the game. The question is, was the unpatched version of BF:42 blocking the idle process from kicking in? I refuse to believe they optimized the code that much in the patch.

[shassouneh 0]

To the best of my understanding, what the System Idle Process does is limit the amount of instructions the CPU has to rip through, which cools it down slightly over a long period of time.

The reality of this is a bit more complex. As you probably already know, modern Operating Systems (Windows and Linux included) give you the "iillusionn" of multi tasking by running one program at a time, only very fast. What this means is say you have 10 processes running. The CPU will run process one for say 5 units of time, then process 9 for say 3 units of time, then process 10 for 6 units of time, so on and so forth. to the human eye it LOOKS like all this stuff is running simultaneously, when in fact every second of time the CPu switches between application hundreds, thousand, or even millions of times!!!

 

Long story short, the System Idle process doesn't do much, and that IS the point. By not having your CPU do much, its temperature drops when windows thinks you don't have a "high" load. Think of the System idle process as Microsoft Windows' way of trying to cool down your CPU by software