Prepare software for modern standby
On entry to modern standby, apps and system software must be made ready for the transition to low-power operation. Powering down the display is the first activity when entering standby. The display is turned off in response to the user pressing the power button, closing the lid, or selecting Sleep from the power button in the Settings charm.
Software preparation phases
After the display is powered off, Windows transitions through a set of phases to prepare apps and system software for achieving low power. The phases are sequential—each phase is a set of activities that must be performed before the phase can be completed and the next phase entered.
The purpose of these phases is to stop or reduce as much software activity on the system as possible. This reduction in activity gives more opportunity for the hardware to enter low-power modes, thereby extending overall modern connected standby battery life.
The following table describes each phase of preparing software for modern standby.
|Topics||Description||Tasks performed||Exited when...||Typical duration (seconds)|
Note This is also the phase where the device waits for the sleep timeout to elapse.
The system is powered on and the screen is turned on. The system is not in standby.
No standby preparation tasks are being performed.
The screen is powered down.
The system is checking for remote desktop connections.
There are no remote desktop sessions connected.
This phase is currently not used by Windows 8 or Windows 8.1.
Process Lifetime Manager (PLM) phase
The system suspends Windows Store apps that are in the foreground.
All foreground Windows Store apps have been suspended and no non-offloaded audio playback is occurring.
The system executes maintenance tasks.
Wait for maintenance tasks to complete if running (most common on AC power).
No system maintenance tasks are running.
Desktop Activity Moderator (DAM) phase
The system pauses desktop applications to reduce their power consumption during standby.
All outstanding power requests have been cleared by applications or the maximum time-out has been reached.
The system notifies registered subscribers that the power manager is entering a low-power, long-resume-latency phase. This is used by some devices as a hint to power down.
Notify registered subscribers.
All registered subscribers have been notified.
Typically, five seconds.
Resiliency notification phase
The network subsystem is notified to enter a low-power mode.
Notify the network subsystem. Network adapters that do not support modern connected standby are turned off (D3).
The network subsystem has been notified.
Typically, less than one second.
The system is ready for the SoC to enter the lowest power mode and remain idle.
The majority of time the system is in standby.
After Windows has entered the resiliency phase, software is considered to be fully prepared for low-power operation. As soon as all devices have entered their low-power modes, the SoC and core chipset will enter the lowest idle power mode, as described in Prepare Hardware for Modern Standby.
Note Currently, no means is available to system designers to change or influence the behavior of these phases—they are a core part of Windows behavior. The details are explained here to aid in system debugging and development.
Desktop activity moderator
The desktop activity moderator (DAM) is the Windows component that is used to pause all desktop applications and throttle the runtime of third-party system services. The purpose of the DAM is to enable basic software compatibility with existing applications and services, but mitigate their impact on battery life during standby.
Windows prevents desktop applications from running during any part of modern standby after completing the DAM phase. Windows allows third-party system services to execute in a throttled mode after completing the DAM phase.