Wake sources

A PC that supports the Modern Standby power model must be capable of waking from standby in response to certain events, even if the platform has entered a very low-power idle state.

This topic describes the types of wake sources that must be able to wake the processor. It also explains which wake events should turn the screen on and which wake events should allow the screen to stay turned off. System integrators should use this information to ensure that their hardware platforms, firmware, and software can configure wake sources to achieve the required behavior.

Overview of Modern Standby user experience for wake

The Modern Standby user experience is designed to model that of a cellular phone. When users finish using their phones, they press the system power button and the cell phone enters sleep mode. The phone remains asleep until the user presses the power button again, or a phone call, email, or instant message is received.

Similarly, when a PC is in Modern Standby, it looks and feels off—the screen is blanked, the system has no visible LED indicators, and there is no acoustic noise. However, a PC in Modern Standby remains on and connected to the Internet, just as the cell phone remains connected to the cellular network. (The Modern Standby PC uses any available network connection—Wi-Fi, mobile broadband (MBB)/cellular, or wired Ethernet.) And the Modern Standby PC, connected or not, also has very long battery life in its screen-off state, just like a cell phone.

Enabling the Modern Standby user experience requires all of the devices and software in the Modern Standby PC to actively and correctly participate in system power management. Achieving long standby battery life is primarily a function of allowing all devices, plus the core silicon or System on a Chip (SoC), to enter a very low-power idle state. During Modern Standby, the networking subsystem stays connected so that the system can wake and instantly respond to incoming emails or VoIP calls. Enabling the real-time nature of Modern Standby is primarily a function of platform devices waking the SoC for the correct events at the correct times.

All wake sources in the Modern Standby PC are expected to be capable of waking the SoC from its deepest idle power state. Some wake sources should be capable of generating a wake signal for an event that would cause the system display to turn on. The difference between waking the SoC and turning on the display is central to delivering the Modern Standby user experience. The following rules govern platform wake behavior:

• Wake source operation and scenarios are the same for all Modern Standby PCs, regardless of whether they are based on the x86 or Arm processor architecture.
• Wake source operation may differ depending on whether the system is plugged in (AC power) or on battery power (DC power). Differences are noted in the tables below.
• Some wake sources are hardware-dependent, e.g. wake on fingerprint or wake on optical disc drive ejection (some Modern Standby systems may not have a fingerprint reader or optical disc drive). Modern Standby systems are recommended to support all wake scenarios for which they have the necessary hardware.

The remainder of this topic describes the different types of wake sources, along with additional information, such as whether the wake source can turn on a device's display, whether it is enabled by default, and any differences in operation depending on whether a device is on AC or DC power.

Most systems enable Connected Standby by default.

Types of wake sources

Real-time clock (RTC) or always-on timer

The core silicon or SoC chip in a Modern Standby platform has one or more timers that are always powered on that so that Windows can schedule future work and place the SoC into a deep idle state. During standby, the always-on timer reliably wakes the SoC as programmed by the OS.

Buttons and lid

The system power button is a very common user-initiated wake source in a Modern Standby platform. All Modern Standby PCs must be designed so that the power button is always enabled to send a wake interrupt to the SoC. To deliver an instant-on experience, the power button must cause the SoC to wake from the deepest idle state without delay. Another common user-initiated wake source on clamshell form factor devices is opening the lid, which wakes the SoC. The Windows button is also able to wake the SoC.

Communications devices

The Wi-Fi, Ethernet, and mobile broadband (MBB) devices are responsible for delivering the real-time and constant connectivity features of Modern Standby. They facilitate wake sources such as Universal Windows Platform (UWP) Applications notifications and syncing and Bluetooth notifications and syncing.

Input devices

We recommend using HIDI2C for input peripherals whenever possible for better power efficiency, but this is not a requirement. If necessary, USB can be used to connect to an input device such as a touchpad, touch digitizer, or pen digitizer. We highly recommend that a precision touchpad be capable of waking the system from deep idle, regardless of whether this device is connected to USB, I2C, or SPI. Pen digitizers must not wake the system from deep idle.

In addition to buttons on the chassis, a Modern Standby PC might have other input devices physically integrated into the system or attached to the system directly or indirectly through a dock. When the user generates input through an input device, it must always wake the SoC from the deepest idle state and cause the display to turn on, unless the lid is closed and input suppression is engaged.

Starting in Windows 11, touch screens may also wake the system from deep idle or S3, however it is not required. OEMs, ODMs and system implementers should be conscious of the additional battery drain that a wake capable touch screen will have while the system is in its respective standby mode."

Voice input

On systems that are Wake on Voice-capable and have a hardware keyword spotter (HW-KWS), voice input of "Hey Cortana" from the user can wake the SoC from the deepest idle state and cause the display to turn on. On systems with Multiple Voice Assistants (MVA) support with an MVA-capable driver, additional voice assistant commands can wake the SoC from the deepest idle state and cause the display to turn on.

Insertion or removal of a connector or device

When the user inserts or removes certain types of connectors or devices, these events can wake the SoC from the deepest idle state and cause the display to turn on.

Windows Update

Windows Update can always wake the SoC from the deepest idle state to scan for updates. It can also wake the SoC to download and install updates and restart a device, depending on a device's power source.

Universal Windows Platform (UWP) Applications

UWP applications can wake the SoC from the deepest idle state to sync and display notifications, depending on a device's power source, notification priority levels, and app-specific user configurations.

Remote Access

Remote Desktop and File Sharing can wake the SoC from the deepest idle state, depending on the target device's power source and networking connection. Remote Desktop can turn on the display on the target system.

Audio

Audio from internal speakers or Bluetooth speakers can wake the SoC, so that audio continues playing even when a device's screen is off.

Environmental context changes

The Modern Standby PC must also respond in real-time to changes in environmental conditions. The common cases are thermal events and power source change events.

Wakes SoC and can turn on display

Buttons and lid

Input devices

Voice input

Insertion or removal of a connector or device

Windows Update

Universal Windows Platform (UWP) Applications

Remote Access

Environmental context changes

Wakes SoC but cannot turn on display

Real-time clock (RTC) or always-on timer

Insertion or removal of a connector or device

Communications devices

Windows Update

Remote Access

Universal Windows Platform (UWP) Applications

Audio

Environmental context changes