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1<?xml version='1.0' encoding="UTF-8"?> 1<?xml version='1.0' encoding="UTF-8"?>
2<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> 2<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.40 2009/08/05 14:51:17 nightmorph Exp $ --> 3<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/power-management-guide.xml,v 1.41 2009/08/12 02:24:57 nightmorph Exp $ -->
4<guide link="/doc/en/power-management-guide.xml"> 4<guide link="/doc/en/power-management-guide.xml">
5<title>Power Management Guide</title> 5<title>Power Management Guide</title>
6 6
7<author title="Author"> 7<author title="Author">
8 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail> 8 <mail link="earthwings@gentoo.org">Dennis Nienhüser</mail>
21 21
22<!-- The content of this document is licensed under the CC-BY-SA license --> 22<!-- The content of this document is licensed under the CC-BY-SA license -->
23<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> 23<!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
24<license/> 24<license/>
25 25
26<version>1.43</version> 26<version>1.44</version>
27<date>2009-08-05</date> 27<date>2009-08-11</date>
28 28
29<chapter> 29<chapter>
30<title>Introduction</title> 30<title>Introduction</title>
31<section> 31<section>
32<body> 32<body>
458</p> 458</p>
459 459
460</body> 460</body>
461</section> 461</section>
462<section> 462<section>
463<title>Setting The Frequency Manually</title> 463<title>Setting The Frequency</title>
464<body> 464<body>
465 465
466<p> 466<p>
467Decreasing CPU speed and voltage has two advantages: On the one hand less 467Decreasing CPU speed and voltage has two advantages: On the one hand less
468energy is consumed, on the other hand there is thermal improvement as your 468energy is consumed, on the other hand there is thermal improvement as your
477section to verify yours is supported. 477section to verify yours is supported.
478</note> 478</note>
479 479
480<p> 480<p>
481It's time to test whether CPU frequency changing works. Let's install another 481It's time to test whether CPU frequency changing works. Let's install another
482tool which is very handy for debugging purposes: <c>sys-power/cpufrequtils</c> 482tool: <c>sys-power/cpufrequtils</c>.
483</p> 483</p>
484 484
485<pre caption="Checking CPU frequency"> 485<pre caption="Checking CPU frequency">
486# <i>emerge cpufrequtils</i> 486# <i>emerge cpufrequtils</i>
487# <i>cpufreq-info</i> 487# <i>cpufreq-info</i>
512governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as 512governor and verify the change with <c>cpufreq-info</c>. If it doesn't work as
513expected, you might find help in the <uri link="#doc_chap8">Troubleshooting 513expected, you might find help in the <uri link="#doc_chap8">Troubleshooting
514section</uri> in the end of this guide. 514section</uri> in the end of this guide.
515</p> 515</p>
516 516
517<p>
518<c>cpufrequtils</c> can operate in an automatic mode (when you use the
519<b>ondemand</b> governor), you can also switch to the <b>userspace</b> governor
520if you want to manually set a specific speed. You can also statically set your
521CPU to its highest or lowest frequency by using the <b>performance</b>
522and <b>powersave</b> governors, respectively.
523</p>
524
525<pre caption="Changing CPU speeds">
526<comment>(Set the highest available frequency)</comment>
527# <i>cpufreq-set -g performance</i>
528<comment>(Set the lowest available frequency)</comment>
529# <i>cpufreq-set -g powersave</i>
530<comment>(Set a specific frequency)</comment>
531# <i>cpufreq-set -g userspace</i>
532# <i>cpufreq-set -f 2.00ghz</i>
533</pre>
534
517</body> 535</body>
518</section>
519<section> 536</section>
520<title>Automated frequency adaption</title> 537<section>
538<title>Other CPU Speed Utilities</title>
521<body> 539<body>
522 540
523<p> 541<p>
524The above is quite nice, but not doable in daily life. Better let your system 542While <c>cpufrequtils</c> may be the best all-around program, there are some
525set the appropriate frequency automatically. There are many different 543other choices available in Portage. The following table gives a quick overview
526approaches to do this. The following table gives a quick overview to help you 544of available CPU speed utilities. It's roughly separated in three categories
527decide on one of them. It's roughly separated in three categories <b>kernel</b>
528for approaches that only need kernel support, <b>daemon</b> for programs that 545<b>kernel</b> for approaches that only need kernel support, <b>daemon</b> for
529run in the background and <b>graphical</b> for programs that provide a GUI for 546programs that run in the background and <b>graphical</b> for programs that
530easy configuration and changes. 547provide a GUI for easy configuration and changes.
531</p> 548</p>
532 549
533<table> 550<table>
534<tr> 551<tr>
535 <th>Name</th> 552 <th>Name</th>
739<c>battery</c> runlevel as well. 756<c>battery</c> runlevel as well.
740</p> 757</p>
741 758
742<pre caption="Starting cpufreqd"> 759<pre caption="Starting cpufreqd">
743# <i>rc-update add cpufreqd default battery</i> 760# <i>rc-update add cpufreqd default battery</i>
744# <i>rc</i> 761# <i>/etc/init.d/cpufreqd start</i>
745</pre> 762</pre>
746 763
747<p> 764<p>
748Sometimes it can be desirable to select another policy than the daemon chooses, 765Sometimes it can be desirable to select another policy than the daemon chooses,
749for example when battery power is low, but you know that AC will be available 766for example when battery power is low, but you know that AC will be available

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