Windows Auto-Sleep

1. Application Power Management Best Practices for Windows Vista
http://www.microsoft.com/whdc/system/pnppwr/powermgmt/PM_apps.mspx
Sleep Idle Timeout
If a system has been idle longer than the sleep idle timeout in the power policy, Windows automatically places the system in the sleep state. Windows uses both user input and processor usage to determine if a system is idle and tracks this information over time.
Generally, applications must prevent the system from entering the sleep state while applications are performing a background task or undertaking an operation that the user expects the system to continue until the operation is complete. Applications might need to prevent the sleep idle timeout in the following scenarios:
· A media application that displays full-screen content or visualizations
· Background applications such as hard disk defragmentation or antivirus utilities while a system scan is in progress
· A media application that records television content
· An application or service that streams content to other devices on the network
· An application such as a Web browser while downloading large files from the internet or network
· Applications that synchronize content to another device or computer

When preventing the sleep idle timeout in their applications, developers must exercise caution because the user expects the system to idle to sleep if it is enabled in power policy. Therefore, applications should prevent the sleep idle timeout only when absolutely necessary.


2. System Sleep Criteria: System Sleep Criteria:
http://msdn.microsoft.com/en-us/library/aa373233%20(VS.85).aspx
If a system has been idle longer than the sleep idle timeout in the power policy, Windows automatically places the system in the sleep state. Windows uses both user input and processor usage to determine if a system is idle and tracks this information over time.


3. Windows Auto-sleepAuto-sleep is supposed to happen during periods of inactivity. It works with system idle timer.As long as the system determines that there is user or application activity, it will not enter sleep. The system can detect certain activities, such as user input or network communications. Windows takes consider many things to determine system is idle(inactive), including
· There is no user input.
· CPU and disk utilization levels.
· The system is not running on battery power.
· No presentation program, such as a slide show or a movie player, is running.
· Things going on in the background
· If you are connected to a broadband connection, that can be picked up as possible network activity
· Audio channel not open
· Modem device not in use
· Others