Root/Documentation/power/apm-acpi.txt

1APM or ACPI?
2------------
3If you have a relatively recent x86 mobile, desktop, or server system,
4odds are it supports either Advanced Power Management (APM) or
5Advanced Configuration and Power Interface (ACPI). ACPI is the newer
6of the two technologies and puts power management in the hands of the
7operating system, allowing for more intelligent power management than
8is possible with BIOS controlled APM.
9
10The best way to determine which, if either, your system supports is to
11build a kernel with both ACPI and APM enabled (as of 2.3.x ACPI is
12enabled by default). If a working ACPI implementation is found, the
13ACPI driver will override and disable APM, otherwise the APM driver
14will be used.
15
16No, sorry, you cannot have both ACPI and APM enabled and running at
17once. Some people with broken ACPI or broken APM implementations
18would like to use both to get a full set of working features, but you
19simply cannot mix and match the two. Only one power management
20interface can be in control of the machine at once. Think about it..
21
22User-space Daemons
23------------------
24Both APM and ACPI rely on user-space daemons, apmd and acpid
25respectively, to be completely functional. Obtain both of these
26daemons from your Linux distribution or from the Internet (see below)
27and be sure that they are started sometime in the system boot process.
28Go ahead and start both. If ACPI or APM is not available on your
29system the associated daemon will exit gracefully.
30
31  apmd: http://ftp.debian.org/pool/main/a/apmd/
32  acpid: http://acpid.sf.net/
33

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