How can I determine which sleep states are available on my Windows Vista machine?

A. You can use the powercfg tool with the /a switch to display the sleep states supported on a machine, as the following example and output show:


C:\>powercfg /a

The following sleep states are available on this system:
Standby ( S1 S3 ) Hibernate Hybrid Sleep
The following sleep states are not available on this system:
Standby (S2)
The system firmware does not support this standby state.

The power states of a machine are:

  • S0: Working. This is the normal state of the computer when switched on.
  • S1: Suspend / Sleeping 1: The CPU suspends activity but retains all its contexts in a very low-power state.
  • S2: Suspend / Sleeping 2: The CPU is powered down and loses its contexts, but the memory retains all of its data.
  • S3: Suspend / Sleeping 3: Same as S2 but devices will need to be reinitialized at the next wake-up.
  • S4: Hibernation / suspend-to-disk: All contexts are written to disk in a hibernation file and the system is powered off (same as S5).
  • S5: Soft-off: Everything has been shut down.

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