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How to change CPU frequency

  1. HikaruGunner

    HikaruGunner New Member

    I have a Jiayu G4 Advanced G4T 2G/32G MTK6589T Quad Core 1.5GHz
    So I downloaded tasker and I want to decrease cpu frequency when the phone is not in use. So I create a task, new action and select misc --

  2. Rukbat

    Rukbat Well-Known Member

    1508000 is just over 1.5GHz, which is what the phone's rated at. The difference in performance between that and 1.5GHz could be measured, but you wouldn't live long enough to actually notice it (even if you were born today). So set the max at 1500000 (1.5GHz) and you won't be pushing it.

    BTW, with most kernels, you can run an app that sets the max and min frequencies (and a couple of other things) without using Tasker (if that's all you're using it for).

    Oh - CPU 0: In Linux, as in most operating systems, numbering starts with 0. So these are the specs for the first CPU. (It may be for all cores, or there may be 4 settings, 0-3, one for each core.)
  3. HikaruGunner

    HikaruGunner New Member

    The options are 1508000, 1209000, 988000, 754000, 497250. So I'll just assume 1508000 is the default clock of this CPU, so I'll just select this.

    I'm using Tasker to save battery, so I'm using it to turn wifi on when I launch a app that requires internet conection (ex: Opera) and disconect it when the same app closes it. Same thing with GPS (turn it on when I'm using a GPS navigation app, and turn it off when the same app closes it).

    As for the CPU, I created a profile to run at max speed when the display is on, and run at 497250 (the lowest selectable CPU frequency) when the display is off. I think it's working because when I benchmark the cpu with antutu software (instead of FULL TEST i only choose CPU to save time, since it's the only component I want to measure) it gives me 3800 points, and when I run the same test BUT with the display off, it gives me only 780 points!

    It would be interesting to know if this affects battery life at all tough, can you recomend me a way to test if the battery is indeed lasting longer?

    Yes that's right I can select between 0-3. Should I leave it at zero?

    Thanks for the help
  4. ooberandy

    ooberandy Well-Known Member

    I remember doing this on an old phone, using this app

    Battery life was indeed improved & the way I tested was just seeing how much battery I had left at the end of the day.

    I'd forgot about this, so might install it again :)
  5. codesplice

    codesplice Elite Recognized Geek Moderator

    Sounds like Rukbat has already given you a pretty good rundown, but there's one thing I'd like to chime in on:

    Most kernels (the ones that I've encountered, at least) don't support different speeds for the different cores, and will instead will take the frequency applied to CPU 0 and apply it to all the other cores as well. So you should be good to just set CPU 0 and ignore the rest :)
  6. HikaruGunner

    HikaruGunner New Member

    I read that other softwares let you modify with CPU voltages to underclock the CPU. Isn't this the same thing I'm doing with Tasker? Or is it something completely different? I'm a little confused about this.

    Thanks for the help guys
  7. codesplice

    codesplice Elite Recognized Geek Moderator

    Voltage is completely separate from frequency. Well, mostly.

    The kernel includes a voltage table which tells the processor how much power should be used at different clock speeds. For instance, my N4 is currently set for 787500uV @ 384000kHz, on up to 1062500uV at 1512000kHz. Undervolting just means adjusting that table to use less power at a given frequency. It is possible to save battery by doing so, but lower voltage may also decrease the stability of the processor. It's a fine balance between lowering the voltage enough to save power, but not so low that you get spontaneous reboots (which consume more power ;) ).
  8. HikaruGunner

    HikaruGunner New Member

    Seems a pretty good idea to undervolt then. Unfortunately, the tab voltages does not appear on SetCpu, so I assume my phone does not allow for this functionality.:mad:

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