Managing Power in Windows Vista
Windows Aero
Managing Power in Windows Vista
Windows Vista introduces four main power management improvements:
- A new power button that encourages the use of power-saving modes—including sleep (also known as S3 mode) on mobile PCs and a new hybrid mode on desktop PCs called Fast S4, which combines sleep and hibernate
- Restrictions on the ability of applications to interrupt sleep transitions
- A new user interface for managing situations in which an application has to block shutdown
- A simpler presentation of power management options
Turning off a mobile PC
The power button on the Start menu is intended to encourage users to take advantage of power-saving modes on their computers, rather than rely on shutdown. Of course, users can always shut down. By default, the power button puts a mobile PC into sleep (S3). This mode turns off most hardware on the mobile PC but maintains the RAM state. The user can quickly resume from standby with the same desktop configuration.
Desktop PCs use a new power-saving mode called Fast S4. In this mode, the system goes into standby, but RAM contents are written to disk, just as they are in hibernate (S4 mode).
New shutdown process
Application developers need to be aware of changes in the shutdown process in Windows Vista. The net result is that when users want to turn off their computers, they're much more likely to get what they ask for.
- Prior to Windows Vista, an application could veto a sleep transition by responding to the PBT_APMQUERYSUSPEND power broadcast. Now, applications cannot veto sleep transitions. (Although this can be changed to the prior behavior through a Group Policy setting.)
- Applications can still veto a shutdown by responding to the WM_QUERYENDSESSION message. However, Windows Vista provides a summary screen that makes it easier for the user to close an application that's blocking shutdown.
- Applications can provide a descriptive string that explains why hey're vetoing shutdown. For more information about the creating the string for the shutdown procedure, see ShutdownBlockReasonCreate()ShutdownBlockReasonCreate().
- Applications that don't have a top-level window—or that hang—are automatically closed when the computer is shutting down.
Simplified power management settings
In Power Options in Control Panel, users can choose the power management behavior that they want. Choices are collected into power management plans, each of which has one of the following designated personalities:
- Balanced
- Power saver
- High performance
Besides clarifying options for users, the personalities make it easier to determine the overall intent of each power plan. Many users will use the default Automatic plan, which uses the Balanced personality. However, users can easily switch among plans and also change settings for a plan.
Power management preferences can change during an application session. Your application can be notified when settings change.
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