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Information on Power States

Technote (troubleshooting)


Problem(Abstract)

TEM defines the following power states in the Power Management product:

Resolving the problem

TEM defines the following power states in the Power Management product:

  • Active - A user is working on the computer ("S0") and is using one of the input devices (specifically the mouse or keyboard). The computer is considered to be using full power in this state.
  • Idle - This state is also considered to be using full power ("S0") but the user is not actively interacting with the system. In many cases, the idle power state is considered wasted electricity since the computer is not using low power modes, but it is not being used.
  • Standby (also known as "Sleep") / Hibernation - Low power mode where the user's working session is saved in memory (S3) or to disk (S4).
  • Power-off - The computer is off (S5).

Most computers follow ACPI specifications, which defines several power states of the computer that are designated as S0-S5. Here are the basics of each of the ACPI power states:

  • Working (S0) - If you are actively using your computer, it is in S0 and using full power (although certain devices might be in lower power modes).
  • Sleep/Standby (S1-S3) - There are 3 different sleep states that progressively save more power. Most computers will use S3 sleep mode, which saves the more power than S1 or S2. In sleep mode, the computer appears to be off, but the contents of memory are preserved so the computer can be quickly awakened (usually with a keyboard or mouse click) without losing work.
  • Hibernation (S4) - Similar to Standby except that the computer's memory is written to the hard disk. When the computer starts again, the memory is restored from disk. Hibernation will typically use slightly less power than standby because the computer does not need to use power to keep memory active, but it will take longer to start the computer because memory will need to be restored from disk.
  • Power-off (S5) - Sometimes called "soft-off", this is the lowest power state in terms of electricity used, although most computers will still use a small amount of electricity when powered off to keep network adapters active to look for Wake-on-LAN packets.

More information on ACPI power states can be found at http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface#Power_States.

Computer state ACPI State Wake-on-LAN controlled by Scheduled Wake-from-Standby possible Resume Process* Typical Power Used*
Powered on S0 n/a n/a n/a Full Power
Standby / Sleep S3 OS settings Yes Computer state in memory (faster resume) Older computers often use more power (30 watts) and newer computers often use much less (<5 watts)
Hibernate S4 BIOS/NIC Settings No Memory must be loaded from disk (med time resume) <2 watts
Powered off S5 BIOS/NIC Settings No Standard boot times (slower resume) <2 watts
* Can vary significantly by computer model.

Historical Number

1667

Document information

More support for: IBM BigFix family

Software version: BES 7.2

Operating system(s): Platform Independent

Reference #: 1506225

Modified date: 11 November 2011


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