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Whilst browsing the interwebs, I found an article here about how to run a Power Efficiency Report. As I wasnt doing anything, I decided to try it and see what it did.

In the results it listed the following four sleep states with true of false next to them showing if my PC supports it;

  • S1
  • S2
  • S3
  • S4

I just wondered, what are the differences between these sleep states?

Thanks

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Thanks for the answers guys. I upvoted both answers, Wil got accepted answer because he set out the answer rather than just copy+paste. –  Connor W Nov 18 '09 at 18:41

2 Answers 2

up vote 22 down vote accepted

S0 - On / Working

The computer is powered up. If supported, power conservation is handled by each device.

S1 - Sleep

CPU is stopped. RAM maintains power. Everything else is off, or in low power mode.

S2 - Sleep

CPU has no power. RAM maintains power. Everything else is off, or in low power mode.

S3 - Standby

CPU has no power. RAM maintains power, refreshes slowly. Power supply reduces power. This level might be referred to as “Save to RAM.” Windows enters this level when in standby.

S4 - Hibernate

Power to most hardware is shut off. Any files in memory are saved to the hard disk in a temporary file. If configured, the NIC will remain on for WOL, or AoL. This level is also known as “Save to disk.”

S5 - Off

Everything is off. No files are saved. If configured, the NIC will maintain power to listen for WOL (Magic) packets. This is known as a shutdown.

Source

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How can I know to which of them my computer is configured when sleep ? –  Royi Namir Jul 10 at 7:15

Excerpt from Wikipedias article on ACPI

  • S0/Working System is on. The CPU is fully up and running; power conservation is on a per-device basis.
  • S1 Sleep System appears off. The CPU is stopped; RAM is refreshed; the system is running in a low power mode.
  • S2 Sleep System appears off. The CPU has no power; RAM is refreshed; the system is in a lower power mode than S1.
  • S3 Sleep (Standby) System appears off. The CPU has no power; RAM is in slow refresh; the power supply is in a reduced power mode. This mode is also referred to as 'Save To RAM'.
  • S4 Hibernate System appears off. The hardware is completely off, but system memory has been saved as a temporary file onto the harddisk. This mode is also referred to as 'Save To Disk'.
  • S5/Off System is off. The hardware is completely off, the operating system has shut down; nothing has been saved. Requires a complete reboot to return to the Working state.

Here's the full article

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I always called S3 "sayonara mode" on Windows XP because it was doubtful that the system would ever get back to S0 and work 100%. Thanks for quoting Wikipedia and saying that. +1 –  Yar Nov 18 '09 at 9:20

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