Hardware Reference
In-Depth Information
Note
For a comprehensive list of PnP device IDs, see the Microsoft Plug and Play ID page at (
ht-
ACPI
ACPI stands for Advanced Configuration and Power Interface, which defines a standard
method for integrating power management as well as system-configuration features
throughout a PC, including the hardware, OS, and application software. ACPI goes far
beyond the previous standard, called
Advanced Power Management (APM
), which con-
sists mainly of processor, hard disk, and display control. ACPI controls not only power,
but also all the PnP hardware configuration throughout the system. With ACPI, system
configuration (PnP) as well as power management configuration are no longer controlled
via the BIOS Setup; instead, they are controlled entirely within the OS.
The ACPI specification was created by Intel, Microsoft, and Toshiba; version 1.0 was re-
leased in 1996. ACPI became one of the major requirements for Microsoft's PC'97 logo
certification program, causing motherboard and BIOS manufacturers to work on integrat-
ing ACPI into systems during that time. Intel integrated ACPI support in chipsets starting
in April 1998 with the PIIX4E southbridge, and Microsoft added ACPI support in Win-
dows starting with the release of Windows 98 (June 25, 1998) as part of what Microsoft
called “OnNow” design. By the time Windows 2000 was released (February 17, 2000),
ACPIhaduniversally replaced APMastheprimarypowermanagement andcontrolinter-
face on new systems.
ACPI enables the system to automatically turn on and off peripherals (such as optical
drives, network cards, hard disk drives, and printers), as well as external devices connec-
ted to the PC (such as DVRs, televisions, telephones, and stereos). ACPI technology also
enables peripherals to turn on or activate the PC. For example, a DVR can turn on the PC,
which could then activate a large-screen television and high-fidelity sound system.
ACPI enables system designers to implement a range of power management features with
various hardware designs while using the same OS driver. ACPI also uses the PnP BIOS
data structures and takes control over the PnP interface, providing an OS-independent in-
terface for configuration and control. Microsoft has included support for ACPI in Win-
dows since Windows 98.
During the system setup and boot process, Windows versions supporting ACPI perform a
series of checks and tests to see whether the system hardware and BIOS support ACPI. If
support for ACPI is either not detected or found to be faulty, the system typically reverts
