Apmstat Overview

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Apmstat.exe: Advanced Power Management Status

This command-line tool provides status information on Advanced Power Management (APM) features.

The output of ApmStat can be helpful in troubleshooting APM problems. The tool reports on APM-related registry entries and on APM BIOS problems.

ApmStat tells you whether a computer has multiple processors and whether it is running in ACPI mode.

Corresponding UI

  • The control panel includes a Power Options program. If APM is installed (enabled or disabled) there will be an APM tab in this program. You can turn APM on and off by selecting the box in this tab. This is the only recommended and supported way to turn APM off. Turning APM on is Plug and Play and on the fly, turning it off requires a reboot. If the tab is absent, the computer is either an ACPI computer or an APM-disabled computer.

  • If APM is turned on, there is a Stand by option under Shutdown in the logon dialog box invoked with CTRL-ALT-DELETE. There might also be a hibernate entry, but that is not related. (Hibernate can work even if neither APM nor ACPI are present.) Standby under APM has the same use as under ACPI.

  • If the battery display is turned on in the Power Options program of Control Panel, a battery status icon appears, and it works similarly to ACPI. Note that APM computers always report a single composite battery, regardless of how many are present. (The unified/composite number is used because this is thought to be more reliable on a wide range of APM BIOSs, and it is simpler.)

  • On most APM computers, pressing the power button or sleep button can put the computer on standby (suspend). Most computers require pressing the power button to resume, although some resume with a keyboard touch. Windows 2000 APM does not support custom power buttons.

Concepts

Advanced Power Management (APM) is an older power management scheme based on an SMI/SMM (hidden hardware) BIOS approach. In APM, most of the functionality is in a computer-specific BIOS that is hidden from the operating system. APM was first widely supported on Windows 95.

Advanced Configuration and Power Interface (ACPI) is the new scheme for power management supported on Windows 98 and Windows 2000. Many computers support both APM and ACPI.

APM on Windows 2000 is intended primarily to support older notebook computers, although it can run on desktop computers. In general, it is preferable to disable APM on desktop computers.

On Windows 2000, APM supports only battery status, suspend, resume, and hibernate. Timer wakeup, wake on LAN, wake on ring, and other APM features are not supported.

ACPI should always be used if a computer has a working ACPI BIOS. Some useful features (timed wakeups, for example) are only available through ACPI on Windows 2000.

If no ACPI BIOS is available or if it does not work well, it might be better to use APM.

ACPI should always be used if a computer has a working ACPI BIOS. Some useful features (timed wakeups, for example) are only available through ACPI on Windows 2000.

If no ACPI BIOS is available or if it does not work well, it might be better to use APM.

System Requirements

  • Windows Server 2003

  • In Windows 2000 Server, APM is disabled.

  • If Windows 2000 does not find a battery installed at startup, as is generally the case with desktop computers, stand-by status is not available. Only power-off status is enabled.

File Required

  • Apmstat.exe

See Also

Concepts

Apmstat Remarks
Apmstat Syntax
Apmstat Examples
Alphabetical List of Tools
Pviewer Overview
Exctrlst Overview
Devcon Overview
Apmstat Overview