I was wondering if anyone is aware of how I can change the CPU Core Voltage of a Raspberry pi using system calls from the terminal. I know that we can do this by setting the over_voltage parameter in /boot/config.txt but I was wondering that since some module reads that file to essentially set the voltage and frequency during boot there might be a way to change this from the terminal. I am using a Raspberry Pi 3B+.

I also know that the frequency of the device can be changed using the files in /sys/devices/system/cpu/cpu0/cpufreq but I am specifically looking to see if we can change the voltage of the device in a similar way from the command line after the boot process.

Thank you for any help and suggestions I can get.

  • "some module reads that file to essentially set the voltage and frequency during boot" -> No, the OS/kernel does not read config.txt at all. It's only used by the GPU firmware/bootloader.
    – goldilocks
    Jan 14 at 21:40
  • Okay, so what are the shell commands? An example, I want to switch the core voltage of 1.2V(default) to 1.1V(per say). Are there any files in /sys which does this?
    – noobcoder
    Jan 15 at 7:38
  • Whoops! All apologies. I missed the nuance there. Or not so nuanced: I conflated the two purposes (previous comment deleted). There is potentially a strong correspondence between them (if the core varies voltage with frequency) but I do not know if it is true of the Pi SoCs and the issue is only tangential to the question.
    – goldilocks
    Jan 15 at 15:01
  • I am not entirely sure if changing the frequency also affects the voltage. Since I can scale the frequency to a lower value or underclock using /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed but when I check the core voltage using vcgencmd measure_volts core, it shows 1.2V. Essentially for any changes in frequency (using sysfs) it shows the same cpu core voltage (what gets set during boot). This is why I am thinking there might be an independent kernel module which can be modified from the terminal to change voltage manually after boot.
    – noobcoder
    Jan 18 at 6:22

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