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

  1. #41

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

    Very nice howto. I've moved it into Tutorials and Tips.
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  2. #42
    Arthur Archnix is offline Grande Half-n-Half Cinnamon Ubuntu
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    I got to the step where you run the script, and it wasn't clear if the script itself started burnMMX or not, so I opened up a new tab and typed "burnMMX". It's not clear to me that it's working or doing anything, it kinda just sits there.

    Anyway, then I ran the script and it counted all the way down to zero, but failed to crash my system. It just stopped and said something about "that's not a valid VID to try". I tried to rerun the script but it gave me and error saying
    Load VIDs from 'phc_tweaked_vids'
    > ERROR: Wrong VID count!
    I've deleted those and am rerunning the script. Everything else appears to be working, and all the steps up to this point have worked great. Any ideas what's going wrong?

  3. #43
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by skinnie View Post
    Hi,first of all thanks for this how to.In windows I have undervolted my T7300 to 0.937v@2.0GHz,and had that undervolt in my last 7.10 installation.
    Now I am running a fresh install of kubuntu 64bit,and when I make the


    it says file or folder inexistant (translation of portuguese).
    Any thoughts?
    Undervolt again would be perfect
    hmmm, first of all, youve got to install the 64bit version of the kernel module, which i dont know if its available

  4. #44
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Arthur Archnix View Post
    I got to the step where you run the script, and it wasn't clear if the script itself started burnMMX or not, so I opened up a new tab and typed "burnMMX". It's not clear to me that it's working or doing anything, it kinda just sits there.
    One thread of burnMMX is started automatically. You can verify this with "top" in a terminal or the gnome system monitor. In case you have a dualcore just start a second thread of burnMMX as described in the howto.

    Quote Originally Posted by Arthur Archnix View Post
    Anyway, then I ran the script and it counted all the way down to zero, but failed to crash my system. It just stopped and said something about "that's not a valid VID to try". I tried to rerun the script but it gave me and error saying

    I've deleted those and am rerunning the script. Everything else appears to be working, and all the steps up to this point have worked great. Any ideas what's going wrong?
    The voltage are calculated with a formula that looks like voltage = a+bx, where a is a base level of voltage witch is increased in x steps with a step size of b.
    The script returning zero means x=0, so you don't need to increase the base voltage for your cpu. So everything should be fine, the script will write 1 instead of zero to its result file and you can use that. In my example I get zeros as well.
    Last edited by Ares Drake; June 2nd, 2008 at 02:55 PM.
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  5. #45
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Sebastral View Post
    The other guide says 'remember: you can not set lower VIDs than the lowest default VID'. is that true?
    I know. it would be horrible news, cause if true it explains why some people don't get battery time improvements.. but is it? or how can I find out? I don't seem to have battery improvements doing office work and the cpu running on lowest speed while the VID went from 7 to 1..

  6. #46
    Arthur Archnix is offline Grande Half-n-Half Cinnamon Ubuntu
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Ares Drake View Post
    The script returning zero means x=0, so you don't need to increase the base voltage for your cpu. So everything should be fine, the script will write 1 instead of zero to its result file and you can use that. In my example I get zeros as well.
    I don't think I made myself clear. The script doesn't do anything. It steps down to zero, stops and says run it again, and then fails to run claiming there is not a valid VID count. It's almost like the script has to fail in order to work, but because it can't make my system crash it returns errors. Almost like saying, check for crash=1, error, crash=0, exiting. This is just a guess. In any event, I can't get it to generate anything because I can only run it once.

    Should I do a hard power off just before it finishes the very last test of VID=0? Maybe that will work?

    Also, it wasn't clear from the comments. Is the acpi module you've supplied for a x86 or x86-64 system? Someone else attached a file, but what was that for? 32 or 64?

    Thanks for the answer regarding the burnMMX.

    EDIT: Do I need to run the script while on battery power?
    Last edited by Arthur Archnix; June 2nd, 2008 at 06:21 PM.

  7. #47
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Arthur Archnix View Post
    I don't think I made myself clear. The script doesn't do anything. It steps down to zero, stops and says run it again, and then fails to run claiming there is not a valid VID count. It's almost like the script has to fail in order to work, but because it can't make my system crash it returns errors. Almost like saying, check for crash=1, error, crash=0, exiting. This is just a guess. In any event, I can't get it to generate anything because I can only run it once.

    Should I do a hard power off just before it finishes the very last test of VID=0? Maybe that will work?
    I'll try to explain again. The cpu voltage is a calculated value. It is calculated
    Code:
     voltage=base voltage + number of steps (=VID) * stepsize
    For Pentium M cpus the base voltage is 700.0 mV and stepsize is 16mV, for Core(2)Duos it is 712.5 mV and stepsize 12.5mV.

    The optmize script lowers the number of steps step by step to see if your cpu is stable with a lower step and thus lower voltage. In your case it reaches zero, that means your cpu is stable with just the base voltage. So it doesn't lock up. It reaches zero even for the highest frequency and as the lower frequencies would need even less voltage and you cannot go below base voltage, the script doesn't need to run for the lower frequencies. As 0 for VID may not work you can just use 1. So you are 1 step above base voltage, that would mean for example for a core2duo 712.5mV+1*12.5mV=725mV.
    Your values are then for example 12:1 10:1 8:1 6:1. (The values before the colon are for the frequency and from my machine, you have to use yours).

    That you can go down to base voltage either means that you are lucky and got a nice cpu or that your acpi is broken and the instruction to lower the voltage gets ignored. Are you positive that the phc-modified acpi-cpufreq is installed correctly? Then maybe your acpi table is broken, I am unfortunately no expert on acpi.

    Quote Originally Posted by Arthur Archnix View Post
    Also, it wasn't clear from the comments. Is the acpi module you've supplied for a x86 or x86-64 system? Someone else attached a file, but what was that for? 32 or 64?
    Both modules are for 32bit.
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  8. #48
    Arthur Archnix is offline Grande Half-n-Half Cinnamon Ubuntu
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Ok, I think I understand now. Thanks for the patient replies. I used your settings applied at boot in rc.local (my values were the same, so I could just use those directly), and after a reboot I show the following:
    arthur@archnix:~$ cat /sys/devices/system/cpu/cpu0/cpufreq/phc_controls
    12:1 10:1 8:1 6:1
    So, it appears that the settings have been applied properly, I suppose if it crashes on my I just reboot in single user mode and increase the multiplier. So, if I edit a video and the system crashes, I can change 12:1 10:1 etc... to 12:2 10:2.. and so on.

    Thanks again,

  9. #49
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Quote Originally Posted by Ares Drake View Post
    I'll try to explain again. The cpu voltage is a calculated value. It is calculated
    Code:
     voltage=base voltage + number of steps (=VID) * stepsize
    For Pentium M cpus the base voltage is 700.0 mV and stepsize is 16mV, for Core(2)Duos it is 712.5 mV and stepsize 12.5mV.

    The optmize script lowers the number of steps step by step to see if your cpu is stable with a lower step and thus lower voltage. In your case it reaches zero, that means your cpu is stable with just the base voltage. So it doesn't lock up. It reaches zero even for the highest frequency and as the lower frequencies would need even less voltage and you cannot go below base voltage, the script doesn't need to run for the lower frequencies. As 0 for VID may not work you can just use 1. So you are 1 step above base voltage, that would mean for example for a core2duo 712.5mV+1*12.5mV=725mV.
    Your values are then for example 12:1 10:1 8:1 6:1. (The values before the colon are for the frequency and from my machine, you have to use yours).

    That you can go down to base voltage either means that you are lucky and got a nice cpu or that your acpi is broken and the instruction to lower the voltage gets ignored. Are you positive that the phc-modified acpi-cpufreq is installed correctly? Then maybe your acpi table is broken, I am unfortunately no expert on acpi.



    Both modules are for 32bit.
    well, thats where i was heading, ive got the module installed correctly (if i get phc_control file it should be fine, right?), yet, i dont see any difference with all voltages on 1, or the default (Which is something like 40). i guess my acpi is not compatible enough...which is too bad, battery life is next to useless . Under windows, it took twice the time to drain it completely.

    this is no show stopper for me, but its annoying none the less. and it might definately be a show stopper for others.

  10. #50
    Arthur Archnix is offline Grande Half-n-Half Cinnamon Ubuntu
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    Re: HowTo: Undervolt your notebook CPU for longer battery life

    Anyone else having trouble resuming from suspend after using this cpufreq module? If I copy the old one back it resumes fine. With this one however, the fan spins up to full and the video never gets restored.

    Can someone confirm?

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