How to undervolt Samsung Galaxy S2?

Overclock and overvolt terms are very common on computer PC. However, this will increase power usage and generate more heat. Not so good to try it on smartphone. So the other ways ~ underclock and undervolt should be better on smartphone like Samsung Galaxy S II, right? Yes, to improve battery life. Underclock may not be so efficient in performance / walt ratio. But undervolt surely will improve battery life while maintain the overall performance speed.

Undervolt Samsung Galaxy S2

For example, by underclock from 1.2 GHz to 1 GHz, speed performance drops 16.67% but voltage usage drops 6% only from 1250 mV to 1175 mV. Therefore, it is better to just undervolt only and keep the highest speed stage. Let’s say by reducing voltage from 1250 mV to 1150 mV at 1.2 GHz speed stage, you will get 8% voltage usage reduction while maintaining 1.2 GHz speed.

How to undervolt Samsung Galaxy S2?

  1. Install custom kernel that support undervolt.
  2. Install SetCPU.
  3. At Voltages tab, select the desire value for each speed stages.
  4. Note – try to reduce 25 mV each time.
  5. Click Apply then.
  6. Run Stress test ~ Stress CPU to test stability (located at Info tab).
  7. That’s all.

Note – Only check ‘Set on Boot’ when you are confident that the undervolted values won’t hang and stable all the time.

Each phone has its own CPU chipset. Other people’s SetCPU voltages settings may not work for you. Therefore, you need to try lot of the settings until you get the lowest voltages and stable for daily use.

  • tarorod

    okay – i just installed setCPU 2.2.4 on my SGSII and unfortunately, there is no Voltages tab when i run it.
    I’d like to undervolt my unit. pls help

    • tarorod

      BTW, i did not installed setCPU via samsung market – i’ve downloaded the APK via XDA

    • Read the post correctly lo. You need custom kernel. Stock kernel does not support voltage adjustment.

      • tarorod

        lol sorry, my fault thanks

  • stan

    Thanks for the useful guide. However, may I know if I need to root my SGS2 first?

  • Mason

    Do you have a link to a kernel that supports under clocking?

    Just got the skyrocket and the battery life is pretty awful. I’m using the stock rom now, but I’ll probably be swapping to something else shortly.

  • Roy

    Hi bro, about the stress test i can find where is it located at.
    Im using s2 with ICS4.0.3
    Thank you

    • Located at Info tab.

      • Roy

        sorry… i could nto find the info tab

        • Please refer to the picture above.

  • Roy

    oh i from set spu i though is from the OS itself, sorry my bad

  • manoj

    Once i set wrong settings and set on boot…can i change it back?

    • Sure manoj. Just load SetCPU and change it back.

      • manoj

        Thank you so much. Could you sugest me the min and max clock speed for
        Galaxy s2-GTI9100…running ICS 4.0.3, XXLPQ. Also, please let me know whats
        The deafult clock speed of GTI9100. I forgot to make a note, before changing.
        Thanks again for ur quick response…


        • 1200 Mhz max and 200 Mhz min.

  • manoj

    Thanks…now if iam uninstalling setcpu…it will take the deafault
    Samsung’s settings right? I want to get rid of it and keep my factery
    Settings samsung provided…..please advice…..
    Becoz after installing goes tosleep sometime…thats the problem for me.

    • Not sure. But it should be. Please consult SetCPU developer to double confirm.

  • Manoj

    Thanks Jayce. I have done below steps and It worked.

    1) Set clock speed 1200 Mhz max and 200 Mhz min.
    2) check ‘Set on Boot’
    3) Reboot the phone
    4)Verify settings again by going to ‘Main’ tab.
    5) From Application, clear data and uninstall.

    Now I don’t have crashing issue.

    Thanks ..