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However, the idle process does not use up computer resources (even when stated to be running at a high percent). Its CPU time "usage" is a measure of how much CPU time is not being used by other threads. In Windows 2000 and later the threads in the System Idle Process are also used to implement CPU power saving.
A chart of recent usage for both of these values is shown. Details about specific areas of memory are also shown. There is an option to break the CPU usage graph into two sections: kernel mode time and user mode time. Many device drivers, and core parts of the operating system run in kernel mode, whereas user applications run in user mode.
Many operating systems, for example Windows, [1] Linux, [2] and macOS [3] will run an idle task, which is a special task loaded by the OS scheduler on a CPU when there is nothing for the CPU to do. The idle task can be hard-coded into the scheduler, or it can be implemented as a separate task with the lowest possible priority.
The concept of CPU-bounding was developed during early computers, when data paths between computer components were simpler, and it was possible to visually see one component working while another was idle. Example components were CPU, tape drives, hard disks, card-readers, and printers.
For example, one can interpret a load average of "1.73 0.60 7.98" on a single-CPU system as: During the last minute, the system was overloaded by 73% on average (1.73 runnable processes, so that 0.73 processes had to wait for a turn for a single CPU system on average). During the last 5 minutes, the CPU was idling 40% of the time, on average.
In some cases, the CPU will shut itself off once passing a thermal limit to avoid permanent damage. But they can also be caused by bus errors introduced by other failing components, like memory or I/O devices. Possible causes include: Poor CPU cooling due to a CPU heatsink and case fans (or filters) that's clogged with dust or has come loose.
In many applications, the CPU and other components are idle much of the time, so idle power contributes significantly to overall system power usage. When the CPU uses power management features to reduce energy use, other components, such as the motherboard and chipset, take up a larger proportion of the computer's energy.
Dynamic frequency scaling (also known as CPU throttling) is a power management technique in computer architecture whereby the frequency of a microprocessor can be automatically adjusted "on the fly" depending on the actual needs, to conserve power and reduce the amount of heat generated by the chip.