does anybody know how to overclock AND underclock your gameboy so you can make it variable?

I have a gameboy that I overclocked
and I underclocked a game boy. with positive results and they work great!
i also circuit bent my guitar effects pedal
and I've seen a video on youtube of a guy who used a 555 timer to help the game not crash
and a variable resistor.

i can't figure it out