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Documentation / power / apm-acpi.txt




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Based on kernel version 3.13. Page generated on 2014-01-20 22:04 EST.

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