Note Third-party programs and services may also be running during system idle time. These programs and services may use more than 10 percent of the computer's CPU and disk resources. This level of CPU and disk utilization may reset the System Idle counter and therefore delay the system from entering standby.
Windows schedules certain maintenance tasks when the following conditions are true:
- The system is idle.
- The system running on AC power.
- Windows XP Service Pack 2 (SP2)
- Windows XP Service Pack 1 ( SP1)
- Windows XP with the hotfix from the following Microsoft Knowledge Base article installed:
Computer does not enter standby mode if Power Options profile is set to standby after 45 or more minutes
- There is no user input.
- CPU and disk utilization levels are less than 10 percent.
- The system is not running on battery power.
- No presentation program, such as a slide show or a movie player, is running.
Note A task that is started by the System Idle Task Scheduler service, such as a virus scan or a disk optimization, may trigger a reset of the System Idle counter.
If a scheduled task runs and, in doing this, uses more than 10 percent of CPU and disk resources for an extended period, the Kernel-mode System Idle Detection thread determines that the system is not idle. Therefore, the System Idle counter is reset to zero. This reset process delays the system from entering standby.
If the following tasks are queued, they can be scheduled to run during system idle time without triggering a reset of the System Idle counter:
- The disk layout task
When you start the computer, the disk layout task is queued to run during system idle time. When the System Idle Task Scheduler service schedules this task, Windows examines the registry to determine when this task was last run. If the disk layout task has not been run during the past three days, the process continues. Otherwise, the process quits. If the process continues, it determines whether there have been many changes to the disk layout since the last time this task was run. The System Idle Task Scheduler service requeues the task after 32 processes are created on the system.
To determine whether there have been significant changes in the disk layout, the System Idle Task Scheduler service examines the scenario files in the Windows\Prefetch folder. These scenario files show which files are used during program startup and during computer startup. If this file-examination process continues, the disk layout is updated. This update process may generate CPU or disk utilization of more than 10 percent. And at this level of CPU or disk utilization, the Kernel-mode System Idle Detection thread resets the System Idle counter.
- The system restore task
This task prepares automatic system restore points to improve system reliability.
- The Help services and data collection task
ID do Artigo: 899975 - Última Revisão: 23 de set de 2011 - Revisão: 1