Changing the clock speed of raspberry pi (underclock)
I have been trying to investigate the effects of changing clock speed in Raspberry Pi in a multi-core system development project. In this regards, I have to change the clock frequency of the Raspberry Pi 3.
As far as I read from the internet, the Raspberry Pi uses dynamic scaling for its clock speed. i.e. when the load is below 100%, it uses clock speed as 600Mhz, when the load is 100% it switches to 1.2Ghz to provide better performance.
So far I've got the following information, yet havent been able to set a constant clock frequency for the Raspberry Pi:
1- Using cpufrequtils package,
cpufreq-set -g userspace
cpufreq-set -f 1.2Ghz
cpufreq-info to see the results
2-
Setting through /boot/config.txt
arm-freq=800
3- Writing into kernel files, such as:
echo 800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
I have yet to understand the exact difference between these three methods, and nor have I been able to set a constant frequency. Since the Raspberry Pi 3, by default can only switch between 600Mhz and 1.2Ghz, I either see 600Mhz or 1.2Ghz when I take a look at the cpu's current clock speed via cpufreq-info.
How can set up different frequencies other than600Mhz and 1.2Ghz, such as changing these values to 750Mhz-1000Mhz or simply making it 750Mhz-750Mhz; in this regard, without having to compile a new kernel.
If there is any missing information regarding question, please comment below and I'll try to provide it.
Any help is greately appreciated.
Cheers,