Game Boy Sound

Written by Jonathan Gevaryahu, with help from many, many others.
lord_nightmare at users d0t sourceforge d0t net
I can also be found on Freenode #gnuboy or EFnet #gameboy and #gbdev
(This document is written in the same style/context as Brad Taylor's very
useful NESSOUND.txt; If you found NESSOUND.txt useful for NES work, I hope
find this just as useful for Gameboy work)

The latest version of this document can (hopefully) always be obtained from:
and from Joshua's mirror at:
and sometime soon, from the mirror at:

All results were obtained by studying prior information available, mainly
(in)famous Pan Docs, additional info added to the pan docs by Martin Korth
NO$GMB fame, info from some of Jeff Frohwein's various tests, and from
information derived from my own experimentation.
Anything UNVERIFIED is an educated guess based on prior knowledge.

also, as Brad Taylor said so well:
"A special thanks goes out to Matthew Conte, for his expertise on
pseudo-random number generation (amoung other things), which allowed for the
full reverse engineering of the NES's noise channel to take place. Without
his help, I would still be trying to find a needle in a haystack, as far as
the noise's method of pseudo-random number generation goes..."
This applies here as well, since the Gameboy's PRNG is very similar to the


< **Introduction** >

The DMG-CPU/GBC-CPU/SGB-CPU (sometimes referred to as the GB-