CPU Usage at Idle

An idling CPU has most of its resources remaining for use.

A computer's CPU usage, monitored by the Task Manager in Windows and the Activity Monitor in OSX, changes as users start and end programs and other processes. While idling, or not running any resource-intensive programs, the usage will decrease but never fully disappear.

Idling

Even when not starting any new programs or running any intensive applications, a computer has up to several dozen small processes running in the background. Normal idling operation will still use several percentage points of available CPU. Even the Task Manager monitoring process may take 1 or 2 percent of the CPU to function.

Monitoring

To monitor an idling CPU in Windows, Right-click on the Task Bar and choose "Task Manager," then select the "Processes" tab. CPU usage will be listed in the corresponding column for each process. In OSX, open the "Aplications/Utilites" folder and select the "Activity Monitor".

Idle Process

Some management views will show a "System" or "System Idle Process" as using large amounts of CPU. This process actually monitors the amount of resources remaining, and a higher percentage means the CPU is largely idling.

References

• Coding Horror: Why is the System Idle Process Hogging All the Resources?
• Microsoft Tech Net: Overview of Performance Monitoring
• O'Reilly Mac Dev Center: What is Activity Monitor (or How to Take Your Mac's Pulse)