Advanced Configuration and Power Interface (ACPI) is an open industry standard developed by Intel, Microsoft, and Toshiba for configuration and power management.
The key element of the standard is power management with two important improvements. First, it puts the OS in control of power management. In the currently existing APM model most of the power management tasks are run by the BIOS, with limited intervention from the OS. In ACPI, the BIOS is responsible for the dirty details of communicating with hardware equipment but the control is in the OS.
The other important feature is bringing power management features currently only available in portable computers to the desktop as well as into servers. Extremely low consumption states, i.e., in which only memory, or not even memory is powered, but from which ordinary interrupts (real time clock, keyboard, modem, etc.) can quickly wake the system, are today available in portables only. The standard should make these available for a wider range of systems.
For ACPI to work the operating system, the motherboard chipset, and for some functions even the CPU, has to be designed for it.
This article (or an earlier version of it) contains material from FOLDOC, used with permission.