How to Underclock CPU?

Hi friends. I want to underclock my cpu but i cant. I used cpu controller apps like setcpu etc. also i give a root permission but doesn't work :/ So do we need a custom kernel ? Anyone know how to make a kernel i found kernel source but i know nothing like Jon Snow :D:D

https://github.com/BalcanGSM/MediaTe...e47073b4696064

I want to close 4 core and change my freq to 1.5 ghz. Thank you. Good day.