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System Idle process is used for measuring how much idle time the CPU is having at any particular time(100% minus the sum of all tasks CPU usage). It will display how much CPU Resources, as a percentage are 'idle' and available for use. One instance of this process operates per CPU, and runs to occupy the processor when other threads are not running. Normally this process should take up at least 90%+ of processor time on average (this is the value in the CPU column).
To understand what the memory usage fields represent, read "Performance fields overview
Edited by quietman7, 22 December 2006 - 02:12 PM.