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Thread: HowTo: Undervolt your notebook CPU for longer battery life

  1. #21
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    Kubuntu 12.04 Precise Pangolin

    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by M4rotku View Post
    I was in step 2.b.1 and I recieved the following error when i entered the command.

    command:
    Code:
    sudo cp /lib/modules/`uname -r`/kernel/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko /lib/modules/`uname -r`/kernel/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko.old
    Error:
    Code:
    cp: cannot stat `/lib/modules/2.6.24-16-generic/kernel/kernel/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.ko': No such file or directory
    If this file doesn't exist, then can I still undervolt? And how would I go about doing so if able.
    I am sorry, I just had a typo in the howto. The path to the module is now corrected, so you might try again
    HowTo: Ask Questions the smart way | keep on rockin'...

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  2. #22
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by stred View Post
    hi all

    my system uses the speedstep.centrino module.. is there a way to force it to use the acpi freq module?

    i have a pentium-m 740 (1.73mhz)

    thnks
    You can try to blacklist the speedstep.centrino module and make the acpi_cpufreq the default to load at boot. However it might be that your notebook has a broken acpi implementation, in which case acpi-cpufreq won't work. So you need to try.

    Maybe it is possible to rmmod speedstep.centrino and to insmod acpi_cpufreq to try it without permanent changes.
    In case that works you need to can automate it.
    HowTo: Ask Questions the smart way | keep on rockin'...

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  3. #23
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Ares Drake View Post
    You can try to blacklist the speedstep.centrino module and make the acpi_cpufreq the default to load at boot. However it might be that your notebook has a broken acpi implementation, in which case acpi-cpufreq won't work. So you need to try.

    Maybe it is possible to rmmod speedstep.centrino and to insmod acpi_cpufreq to try it without permanent changes.
    In case that works you need to can automate it.
    you are correct, simple blacklisting and adding acpi-cpufreq to etc/modules worked like a charm.. also the script did very nice job..

    voltages before-after:
    "41 32 25 18"-> "14 7 3 1"

    that's huge difference.. especially in full load i am 10-15 deggres down(difficult to tell cause the fan rans now at different speeds)

    thank you very much sir.
    Last edited by stred; May 24th, 2008 at 11:19 AM.

  4. #24
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by stred View Post
    that's huge difference.. especially in full load i am 10-15 deggres down(difficult to tell cause the fan rans now at different speeds)
    That's not that difficult to tell, just install sensors-applet and you'll have your CPU temperature displayed on your desktop!
    Code:
    sudo apt-get install sensors-applet
    rightclick on a GNOME panel and select "+ Add to panel"
    Nobody was born with linux knowledge!
    Here's my experience with Ubuntu linux on laptops: http://linux.aldeby.org

  5. #25
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by aldeby View Post
    That's not that difficult to tell, just install sensors-applet and you'll have your CPU temperature displayed on your desktop!
    Code:
    sudo apt-get install sensors-applet
    rightclick on a GNOME panel and select "+ Add to panel"
    thnks for your answer but i have allready done that..

    i didnt explain well my thoughts before..

    what i meant is that before in full load i had 62 degrees and fan at 60% approximately

    now in full load i am in 52 degrees but fan is at 30-35% so it's difficult to estimate the gains in lower heat produced cause of the different fan speeds.

    the major difference is in noise.. now even in full load the system is allmost silent..
    Last edited by stred; May 24th, 2008 at 12:14 PM.

  6. #26
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    ive got an everex stepnote SA2053T notebook.

    ive decided to give this a go, it comes with an intel CPU T2080 dual core thingy.

    ran the script, and it didnt hang the computer at all.

    so i ended with these settings.


    Code:
    $ cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls 
    13:2 10:1 8:1 6:1 1:1 1:1 1:1 1:1 2:1 2:1
    is this ok? or is somehow the cpu ignoring the new values?
    my script said something like this:
    Code:
    Default VIDs: 40 32 27 21 134 134 134 134 134 134 
    Current VIDs: 2 1 1 21 134 134 134 134 134 134
    which seems to set a higher VID for lower freqs? something doesnt add up...

    when test started cpu jumped to a new high of 66C, and fan at full speed. it did start scaling down to 55C till it reached a VID of 0.

    then the script exited, and (there seems to be a bug), files it created ended up empty.
    i deleted the files, ran the script again, and killed the process (allowed it to generate valid files), then edited the file with the tweaks, and gave the first value a 0 (my working value). then the script ran all tests no problems.


    the thing is.....how do i know if its working? cpu fan turns on at 60degrees and shuts down at 49degrees, so its just the same everytime. gonna test battery life, but i dont expect this to work, gonna post after..


    EDIT: battery life is the same. dead at 1hr, the battery led on the notebook starts blinking. so i guess the notebook isnt undervolting. or am i missing something out?
    Last edited by eldragon; May 24th, 2008 at 03:49 PM. Reason: added more info

  7. #27
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    I have downloaded the precompiled module for kerner 2.26.24-17-generic but it doesnt load...

    when i try insmod it sais:
    insmod: error inserting 'acpi-cpufreq.ko': -1 Invalid module format

  8. #28
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    2.6.24-17-generic kernel acpi_cpufreq file (32-bit x86 processor compiled version):

    Try this attached acpi_cpufreq file for all those who have the upgraded 2.6.27-generic kernel installed. I'm afraid the one that's originally posted does not work for most people.

    Anyways, thanks for the help. I went from an idle 24 watts with 2 hours of battery life to 12.8 watts with 4 hours of battery life! (I used Intel's powertop application fyi)
    Attached Files Attached Files
    Last edited by krlhc8; May 27th, 2008 at 05:42 PM. Reason: wrong kernel, 32-bit, powertop

  9. #29
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by krlhc8 View Post
    Anyways, thanks for the help. I went from an idle 24 watts with 2 hours of battery life to 12.8 watts with 4 hours of battery life!
    Are you sure this is correct? I can't for the life of me find the link (it must have been somewhere on lesswatts.org but, I can never find the useful stuff I've previously found on it (I really think they hide it from me after I've seen it)) but, for example, on my processor, I believe it uses like 13W in the C0 state and like 3.2W in the C3 state. I don't see how it would be possible to cause an average of 11W decrease in power unless all the C states were running at the normal C3 wattage (which seems impossible because that wattage is essentially the equivalent of "the CPU is turned off").

    I still want to try this but, I'd love to see some scientific evidence that this is actually really useful for power savings. I'm a power savings fanatic but, I don't like to try potentially dangerous things without understand the risk/benefit.

    Edit:
    I asked a similar question in http://ubuntuforums.org/showpost.php...0&postcount=14. If someone could do that and provide hard numbers I'd be greatly pleased.
    Last edited by sdennie; May 27th, 2008 at 10:53 AM.
    Don't try to make something "fast" until you are able to quantify "slow".

  10. #30
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by krlhc8 View Post
    I'm afraid the one that's originally posted does not work for most people.
    Code:
    acpi-cpufreq.ko: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
    It probably mainly works for those people running 64 bit kernels
    Linux user since Slackware 3.4

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