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

  1. #111
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    Mar 2008
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    Arrow Re: HowTo: Undervolt your notebook CPU for longer battery life

    From my experience undervolting lowers your temperature by a few (~3-8 °C) degrees depending on the the CPU load, ...

    I think you're unreasonable expecting figures as high as 15 °C.

    Most the time it's only a matter of a few degrees to get those laptop fans to stop and that's what my main interest was when I started using NHC (windows) a few years back.

    Unfortunately in Ubuntu my fan still runs about 85% of the time but at least it isn't running 100% and maybe it'll change to the better in the future (... it definitely will with the next laptop ...)

    Also undervolting NEVER had any effect on my harddrive temperature (and I've undervolted numerous laptops and even my fileserver running on a Dothan mATX-board).
    Last edited by excogitation; June 26th, 2008 at 10:32 AM.

  2. #112
    Join Date
    Aug 2006
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    841

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

    doing a dmesg i get the following concerning acpi_cpufreq:
    acpi_cpufreq: no version for "struct_module" found: kernel tainted.

    does anyone know what that means?
    Last edited by eldragon; June 26th, 2008 at 02:07 PM.

  3. #113
    Join Date
    Jun 2008
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    1

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

    Ok, let me start off by saying that I'm a total Linux newbie. This is my first Ubuntu install and I'm a big fan for the most part. However, I'm interested in undervolting because my CPU fan is always blowing and my laptop does run hotter under ubuntu as compared to XP (I'm dual booting).

    So, I looked at the guide and managed to compile and install the PHC thing. I ran the script as well as burnMMX concurrently, but the script counted all the way down to 0 and then crashed. So, going on the advice of others in this thread, I set the values all to 19 and put them in the rc.local file. Unfortunately, this caused my Ubuntu to hang. It loads at boot, then just when it normally goes to the login screen, it just stops with a black screen and is unresponsive. when i went to the recovery boot, and edited out the "echo" commands, ubuntu boots as normal, which is to say, overly warm with the fan always blowing.

    Here is some extra information in case it helps:
    Ubuntu 8.04 64-Bit
    Lenovo X61 laptop
    Core2Duo T8300 2.4 Ghz
    4GB RAM

    and here is what I put into my rc.local file (I upped the 19 to 21 to try and boot with it again, no luck):
    echo "13:21 12:21 10:21 8:21 6:21 136:21" > /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
    echo "13:21 12:21 10:21 8:21 6:21 136:21" > /sys/devices/system/cpu/cpu1/cpufreq/phc_controls

    So, anyone have any ideas? I am totally at a loss as to what to do next. Thank you all for being so kind and helpful so far, and any help anyone could give me would be appreciated!

  4. #114
    Join Date
    Feb 2007
    Location
    India
    Beans
    291
    Distro
    Ubuntu 7.10 Gutsy Gibbon

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

    Quote Originally Posted by mrpeaches View Post
    Ok, let me start off by saying that I'm a total Linux newbie. This is my first Ubuntu install and I'm a big fan for the most part. However, I'm interested in undervolting because my CPU fan is always blowing and my laptop does run hotter under ubuntu as compared to XP (I'm dual booting).

    So, I looked at the guide and managed to compile and install the PHC thing. I ran the script as well as burnMMX concurrently, but the script counted all the way down to 0 and then crashed. So, going on the advice of others in this thread, I set the values all to 19 and put them in the rc.local file. Unfortunately, this caused my Ubuntu to hang. It loads at boot, then just when it normally goes to the login screen, it just stops with a black screen and is unresponsive. when i went to the recovery boot, and edited out the "echo" commands, ubuntu boots as normal, which is to say, overly warm with the fan always blowing.

    Here is some extra information in case it helps:
    Ubuntu 8.04 64-Bit
    Lenovo X61 laptop
    Core2Duo T8300 2.4 Ghz
    4GB RAM

    and here is what I put into my rc.local file (I upped the 19 to 21 to try and boot with it again, no luck):
    echo "13:21 12:21 10:21 8:21 6:21 136:21" > /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
    echo "13:21 12:21 10:21 8:21 6:21 136:21" > /sys/devices/system/cpu/cpu1/cpufreq/phc_controls

    So, anyone have any ideas? I am totally at a loss as to what to do next. Thank you all for being so kind and helpful so far, and any help anyone could give me would be appreciated!
    Please refer to http://ubuntuforums.org/showpost.php...0&postcount=91 to see how I got the 19 value for MY system. Find the correct value for your system in a similar way.

  5. #115
    Join Date
    Mar 2007
    Location
    Italy
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    16
    Distro
    Ubuntu

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

    Quote Originally Posted by excogitation View Post
    From my experience undervolting lowers your temperature by a few (~3-8 °C) degrees depending on the the CPU load, ...

    I think you're unreasonable expecting figures as high as 15 °C.
    I think that it depends on cpu. For example, with my T5500 i get impressive result. Before the undervolting, when playing Civ4 with Wine, my cpu go always 97-99 degree. Now i get an impressive 75-85 ... This is very reasonable result.

    Quote Originally Posted by excogitation View Post
    Most the time it's only a matter of a few degrees to get those laptop fans to stop and that's what my main interest was when I started using NHC (windows) a few years back.

    Unfortunately in Ubuntu my fan still runs about 85% of the time but at least it isn't running 100% and maybe it'll change to the better in the future (... it definitely will with the next laptop ...)
    If you want to manage the fan noise, you probably need to recompile your DSDT table, when i do it the fan lower the noise a lot. I don't remember the link, but i found a guide in this forum on how to do that.

  6. #116
    Join Date
    Sep 2005
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    24
    Distro
    Ubuntu 11.04 Natty Narwhal

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

    Do anyone know how to patch cpufreq in 26.25.9 kernel? Currently in svn only got patch for 26.24

  7. #117
    Join Date
    Apr 2005
    Beans
    6

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

    yes (I've test it on 2.6.25.8 vanilla), with the Teknohog PHC patch. http://howflow.com/tricks/undervolt_..._kernel_2_6_25

    But I didn't succeed on the intrepid kernel... (2.6.26rc6 with ubuntu patches)

  8. #118
    Join Date
    May 2008
    Beans
    1

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

    Core 2 Duos should have a min voltage of 15. The minimum for Core 2's is 0.9V, so 712mV + 15*12.5mV. This is a documented lowest voltage.

    As for the 136: xx number people are seeing, this is a setting available for many of the 800MHz FSB Core 2 Duo's. Typically the lowest multiplier is 6, and for a 800MHz quad-pumped FSB CPU, that equates to 6*200MHz = 1.2GHz. However these 800MHz Core 2 Duos can also drop the FSB. At its lowest operating power state, it downclocks to 8 multiplier * 100MHz FSB (400MHz quad-pumped), or 800MHz. That's why it's listed as the last entry. The 136 number is just the represenation of that power state. I'd go out on a limb and say that every 800MHz FSB Core 2 Duo should be able to do that state at 136:15 (or 0.9V i.e. the lowest operating voltage).

  9. #119
    Join Date
    Sep 2005
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    24
    Distro
    Ubuntu 11.04 Natty Narwhal

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

    Quote Originally Posted by Tao View Post
    yes (I've test it on 2.6.25.8 vanilla), with the Teknohog PHC patch. http://howflow.com/tricks/undervolt_..._kernel_2_6_25

    But I didn't succeed on the intrepid kernel... (2.6.26rc6 with ubuntu patches)
    that works great on 2.6.25.9, Thanks!

  10. #120
    Join Date
    Oct 2007
    Location
    Here
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    476
    Distro
    Ubuntu 8.10 Intrepid Ibex

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

    Ok guys,

    I've tried to do this several times now and I think I officially qualify as the least competent person ever to view this thread because it seems that everyone else is able to do this.

    Would anyone be willing to work with me through private messages or AOL IM or Skype to give me step by step instructions.

    It keeps going wrong and I think I know why, but I have no clue what to do about it and I am just really confused at this point. I would've given up by now but my computer really needs to be undervolted.

    Much thanks in advance,
    M4rotku
    ~ Sanity is the sign of an unused mind.
    ~ I poked a badger with a spoon!

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