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When a computer is in sleep mode, it does not perform a task and appears to be turned off. However, it does not turn off, but keeps the memory status. S0, S1, S2, S3 and S4 are the four power states, of which S1, S2, S3 and S4 are the three sleep states. Each subsequent sleep state, from S1 to S4, is further turned off from the computer. S5 is the classic stop state.
System sleep state
In this article, we see the different system sleep states in Windows. MSDN explains this quite well.
System Power State S0 – This is the operating state in which your Windows PC is awake. This is not a sleep mode.
System Power State S1 – In this sleep mode, the CPU stops and your computer is in sleep mode. If the following S3 state is supported, this S2 state is the default state on most hardware. The processor clock is off and the bus clocks are stopped. In this state, the power consumption can be between 5 and 30 watts.
System Power State S2 – This state is similar to S1, except that the CPU context and system cache content are lost because the processor loses performance.
System Power State S3 – In this state, data or context is stored in RAM and hard disks, fans, etc. are stopped. Power consumption is generally less than 5 watts. Wake-On-LAN is supported by S3 (Sleep) or S4 (Hibernate) under Windows 10/8.
System Power State S4 – In this state, the data or context is stored on the hard disk. It is also called Hibernate state and is useful for laptops. Your PC stores the RAM contents on the hard disk. The equipment turns off all appliances. However, the operating system context is maintained in a Hibernate file that the system writes to disk before switching to S4. After rebooting the charger, it reads this file and jumps to the previous system location. The power consumption is again below 5 watts.
Connected Standby State
In Windows 10/8 there is a new state called Connected Standby State.
Connected Standby brings the smartphone power model to the PC. It delivers the instant and instant user experience that users expect from their mobile phones. And like on the phone, Connected Standby keeps the system up-to-date, up-to-date and accessible whenever an appropriate network is available. Windows 8 supports connected standby on low-power PC platforms that meet certain Windows certification requirements. In connected standby mode, the S3 state is deactivated and an additional voltage state known as the S0 Low Power Idle is activated. Connected backup systems include Windows RT systems and some other Windows 8 systems.
The’Slide To Shut Down’ function in Windows 8.1/10 only works if the hardware supports the’Connected Standby’ state.
How Connected Standby differs from Sleep and Hibernate
(1)(1)Sleep and Hibernate are system-wide coordinated sleep states. When the operating system reaches or exits one of these states, it must transfer the system in a coordinated manner between applications, services, drivers, devices and firmware. These transitions require coordination and processing across many layers of the system, many of which are provided by third parties. Therefore, these transitions can be relatively long and prevent transitions from being close to the user.
Connected Standby is neither a sleep state nor a fully coordinated system-wide power state transition. In Sleep Mode connected, the system is always on, but the display is off and the system is idle as much as possible. The aim is to provide a seamless on/off experience and constant connectivity with the same long battery life. Systems that support connected sleep sleep do not support sleep (or ACPI S3) because connected sleep effectively replaces the sleep experience. Systems connected in standby-enabled mode running on x86 platforms support Hibernate. Hibernate is not supported on ARM-based platforms.
Learn more about the connected sleep state in this Microsoft document.
Check if your Windows computer supports the connected sleep state.