Overview of Advanced Power Management (APM) and Advanced Configuration and Power Interface (ACPI) in Windows XP

This article contains a brief overview of power management in Windows. Windows supports both Advanced Power Management (APM) and Advanced Configuration and Power Interface (ACPI) power management.

Windows supports ACPI-compliant BIOS versions, and also some BIOS versions based on APM and Plug and Play designs.

ACPI is an open industry specification that defines a flexible and extensible hardware interface for the motherboard. Software designers use this specification to integrate power-management features throughout a computer system, including hardware, the operating system, and programs. This integration enables Windows to determine which programs are active, and to handle all of the power-management resources for computer subsystems and peripherals.

APM consists of one or more layers of software that support power management in computers with power-manageable hardware. APM defines the hardware-independent software interface between hardware-specific power-management software and an operating system power-management policy driver. It masks the details of the hardware, allowing higher-level software to use APM without any knowledge of the hardware interface.

For information about which ACPI-based BIOS versions are ACPI-compliant, check the Hardware Compatibility List (HCL) for Windows.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information about compatible hardware for Windows, consult the Windows Hardware Compatibility List (HCL). This list is a compilation of computers and computer hardware that have been extensively tested with Windows for stability and compatibility. Microsoft Product Support Services uses the HCL to determine whether or not a computer is supported for use with the Windows operating system. The latest HCL is available from the following Microsoft Web site: