Idle Processor Time

From Unofficial BOINC Wiki

[edit] General

The amount of time that a Central Processing Unit spends doing nothing. Most computers spend a considerable amount of time quite literally doing nothing useful at all. When a computer has nothing to do, this time is spent doing what is called a "busy-wait".

In this state, the computer looks at its list of things to do, and if there is nothing to do, it pauses for a moment, and then checks again. Tasks can be added to this list of things to do, and are added as they occur. They are also added with a priority indicating the importance of the task.

For example, servicing an interrupt from the user is a fairly high priority task, but there are others, like updating internal clocks that are even more important. So, when you type a key, that generates an "interrupt" which the computer "services", then it waits for something else to happen. Because processors are so fast, they can do many things and still be "bored" (just like a teenager).

Because of this, we can "set-aside" a whole priority for things that we want to take place in the background when the computer has nothing else to do ...

And this is the essence of the whole concept of Distributed Computing, use those idle moments of processor time, and put them to work. Because these tasks are performed at a low, or "Idle" Priority, they take nothing away from the user, but gracefully surrender the time to the higher priority tasks as needed.