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Thread: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

  1. #1
    Join Date
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    Dapper Drake Testing/

    Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    As you may have noticed, Pentium M processors support Speedstep. For whatever reason, Intel left Speedstep out of the budget Celeron M processors. But you're in luck! You can get CPU frequency scaling on Celeron M and Pentium 4 processors.

    First off, you need to insert the p4_clockmod module. Open a terminal and do
    Code:
    sudo modprobe p4_clockmod
    This shouldn't give any feedback.

    To make this module load every boot, add it to /etc/modules with your favorite editor ...it should look something like this
    Code:
    # /etc/modules: kernel modules to load at boot time.
    #
    # This file contains the names of kernel modules that should be loaded
    # at boot time, one per line. Lines beginning with "#" are ignored.
    
    p4_clockmod
    Now, as for the actual scaling, you have a few choices. As far as I know, the two more popular CPU scaling daemons are cpufreqd and powernowd. cpufreqd is very configurable and I'm not going to go into it here. I'm sure there are better guides for cpufreqd out there than what I can whip up. The other option (and my preference) is powernowd. Basically, powernowd will scale back your clockspeed when crunching is low, and if it needs more processign power, will scale the clockspeed back up. Check out the man page for more in-depth information.

    Edit: since this post, through various research, it seems that this doesn't really confer significant power savings. I ended up just not bothering, as it merely hampered performance for little or no benefit
    Last edited by krazykit; October 6th, 2009 at 08:27 PM. Reason: updated info

  2. #2
    Join Date
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    Vercelli, Italy
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    Ubuntu 6.10 Edgy

    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    Thank you very much krazykit, this thing was driving me crazy.

    Bye

  3. #3
    Join Date
    Aug 2007
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    Florence, SC, USA
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    Ubuntu 7.04 Feisty Fawn

    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    krazykit, you are a genius. thank you so much for posting this.

  4. #4
    Join Date
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    Victoria, BC Canada
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    Ubuntu 12.04 Precise Pangolin

    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    Hi,

    I'm new to Linux and this is only my 3rd install but I just tried this on my HP dv2402ca (Celeron M 520 @ 1.6 MHz) and the first step:

    $ sudo modprobe p4_clockmod

    resulted in this message:

    FATAL: Error inserting p4_clockmod (/lib/modules/2.6.20-16-generic/kernel/arch/i386/kernel/cpu/cpufreq/p4-clockmod.ko): No such device

    Any suggestions or help would be greatly appreciated!

    Thanks,
    Mike

  5. #5
    Join Date
    Apr 2007
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    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    You don't have a processor supported by this module. This is why this error shows up.

  6. #6
    Join Date
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    Ubuntu 9.04 Jaunty Jackalope

    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    (old thread)
    I've got a good ol' Pentium 4 2.8 GHz desktop processor, and I got the p4_clockmod to work. However, all it seems to do is reduce performance, but the CPU temperature, and I assume therefore also power consumption, stays the same. Is there any way to change this, or is my processor too old?

    Oh, and thank you very much for the guide.


    Edit: after some more reading I have discovered that the primary use for p4_clockmod is to reduce the temperature when the computer is working at full load, ie it won't get as hot maxed out on 700 MHz as on 2.8 GHz, though of course performance suffers. Which leads me to another question; would it be possible to govern the frequency based on the temperature?
    Last edited by ProteinPappa; November 22nd, 2008 at 01:21 AM.

  7. #7
    Join Date
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    Ubuntu 10.10 Maverick Meerkat

    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    Anyone know how this works/performs under Ubuntu Karmic (9.10) ?

  8. #8
    Join Date
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    Re: Howto: CPU Frequency Scaling on Celeron M and Pentium 4 processors

    It should work identically; that is, no or insignificant power savings, just performance loss. Don't bother.

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