this is from the kernel config
"ACPI Support (ACPI)
Advanced Configuration and Power Interface (ACPI) support for
Linux requires an ACPI compliant platform (hardware/firmware),
and assumes the presence of OS-directed configuration and power
management (OSPM) software. This option will enlarge your
kernel by about 70K.
Linux ACPI provides a robust functional replacement for several
legacy configuration and power management interfaces, including
the Plug-and-Play BIOS specification (PnP BIOS), the
MultiProcessor Specification (MPS), and the Advanced Power
Management (APM) specification. If both ACPI and APM support
are configured, whichever is loaded first shall be used.
The ACPI SourceForge project contains the latest source code,
documentation, tools, mailing list subscription, and other
information. This project is available at:
<
http://sourceforge.net/projects/acpi>
Linux support for ACPI is based on Intel Corporation's ACPI
Component Architecture (ACPI CA). For more information see:
<
http://developer.intel.com/technology/iapc/acpi>
ACPI is an open industry specification co-developed by Compaq,
Intel, Microsoft, Phoenix, and Toshiba. The specification is
available at:
<
http://www.acpi.info>
"