Part 1: Power Management Basics

Because of the need to integrate hardware features with software management, today’s computer system power management framework is defined by an open industry specification known as ACPI. ACPI, or the Advanced Configuration and Power Interface specification[1], is an operating system-based scheme for managing system power features and is intended to replace the familiar BIOS-based scheme known as APM (Advanced Power Management).

ACPI is a comprehensive solution that discusses both hardware and software aspects of computer system power management, and how they should interact with one another. You can find the 4.0a specification at:

http://www.acpi.info/spec.htm

Note the diagram on page 24 of the introduction entitled "OSPM/ACPI Global System". It does a nice job of providing an overview of the system components involved and how they interact with one another.

(Quote from the link above: "The Advanced Configuration and Power Interface Specification, Revision 4.0a describes the structures and mechanisms necessary to design operating system-directed power management and make advanced configuration architectures possible. ACPI applies to all classes of computers. If you want to design and build an ACPI-compatible system, you need the ACPI Specification.")

References:
[1] Advanced Configuration and Power Interface Specification, Revision 4.0a, April 5, 2010.