To the user, the system appears to be either on or off. There are no other detectable states. However, the system supports multiple power states that correspond to the power states defined in the Advanced Configuration and Power Interface (ACPI) specification
. There are also variations of these states, such as hybrid sleep and fast startup.
System power states describe the power consumption of the system as a whole. The operating system supports six system power states, referred to as S0 (fully on and operational) through S5 (power off). Each state is characterized by the following:
- Power consumption: how much power does the computer use?
- Software resumption: from what point does the operating system restart?
- Hardware latency: how long does it take to return the computer to the working state?
- System hardware context (such as the content of volatile processor registers, memory caches, and RAM): how much system hardware context is retained? Must the operating system reboot to return to the working state?
State S0 is the working state. States S1, S2, S3, and S4 are sleeping states, in which the computer appears off because of reduced power consumption but retains enough context to return to the working state without restarting the operating system. State S5 is the shutdown or off state.
A system is waking
when it is in transition from the shutdown state (S5) or any sleeping state (S1-S4) to the working state (S0), and it is going to sleep when it is in transition from the working state to any sleep state or the shutdown state. Some devices can wake the system from a sleeping state when certain events occur, such as an incoming call to a modem. In addition, on some computers, an external indicator tells the user that the system is merely sleeping.
With each successive sleep state, from S1 to S4, more of the computer is shut down. All ACPI-compliant computers shut off their processor clocks at S1 and lose system hardware context at S4 (unless a hibernate file is written before shutdown), as listed in the sections below. Details of the intermediate sleep states can vary depending on how the manufacturer has designed the machine. For example, on some machines certain chips on the motherboard might lose power at S3, while on others such chips retain power until S4. Furthermore, some devices might be able to wake the system only from S1 and not from deeper sleep states.
For more information, see:
||The system is fully usable. Hardware components that are not in use can save power by entering a lower power state.
Maximum. However, the power state of individual devices can change dynamically as power conservation takes place on a per-device basis. Unused devices can be powered down and powered up as needed.
System hardware context
All context is retained.
|Sleep (Modern Standby)
||S0 low-power idle
||Some SoC systems support a low-power idle state known as Modern Standby. In this state, the system can very quickly switch from a low-power state to high-power state, so that it can respond quickly to hardware and network events. Systems that support Modern Standby do not use S1-S3.
|The system appears to be off. Power consumed in these states (S1-S3) is less than S0 and more than S4; S3 consumes less power than S2, and S2 consumes less power than S1. Systems typically support one of these three states, not all three.
In these states (S1-S3), volatile memory is kept refreshed to maintain the system state. Some components remain powered so the computer can wake from input from the keyboard, LAN, or a USB device.
Hybrid sleep, used on desktops, is where a system uses a hibernation file with S1-S3. The hibernation file saves the system state in case the system loses power while in sleep.
S1 Power consumption
Less consumption than in S0 and greater than in the other sleep states. Processor clock is off and bus clocks are stopped.
S1 Software resumption
Control restarts where it left off.
S1 Hardware latency
Typically no more than two seconds.
S1 System hardware context
All context retained and maintained by hardware.
S2 Power consumption
Less consumption than in state S1 and greater than in S3. Processor is off. Bus clocks are stopped; some buses might lose power.
S2 Software resumption
After wake-up, control starts from the processor's reset vector.
S2 Hardware latency
Two seconds or more; greater than or equal to the latency for S1.
S2 System hardware context
CPU context and system cache contents are lost.
S3 Power consumption
Less consumption than in state S2. Processor is off and some chips on the motherboard also might be off.
S3 Software resumption
After the wake-up event, control starts from the processor's reset vector.
S3 Hardware latency
Almost indistinguishable from S2.
S3 System hardware context
Only system memory is retained. CPU context, cache contents, and chipset context are lost.
||The system appears to be off. Power consumption is reduced to the lowest level. The system saves the contents of volatile memory to a hibernation file to preserve system state. Some components remain powered so the computer can wake from input from the keyboard, LAN, or a USB device. The working context can be restored if it is stored on nonvolatile media.
Fast startup is where the user is logged off before the hibernation file is created. This allows for a smaller hibernation file, more appropriate for systems with less storage capabilities.
Off, except for trickle current to the power button and similar devices.
System restarts from the saved hibernate file. If the hibernate file cannot be loaded, rebooting is required. Reconfiguring the hardware while the system is in the S4 state might result in changes that prevent the hibernate file from loading correctly.
Long and undefined. Only physical interaction returns the system to the working state. Such interaction might include the user pressing the ON switch or, if the appropriate hardware is present and wake-up is enabled, an incoming ring for the modem or activity on a LAN. The machine can also awaken from a resume timer if the hardware supports it.
System hardware context
None retained in hardware. The system writes an image of memory in the hibernate file before powering down. When the operating system is loaded, it reads this file and jumps to its previous location.
||The system appears to be off. This state is comprised of a full shutdown and boot cycle.
Off, except for trickle current to devices such as the power button.
Boot is required upon awakening.
Long and undefined. Only physical interaction, such as the user pressing the ON switch, returns the system to the working state. The BIOS can also awaken from a resume timer if the system is so configured.
System hardware context
||The system is completely off and consumes no power. The system returns to the working state only after a full reboot.
This tutorial will explain and show you how to see the sleep states available on your Windows 10