#gameboy #diassembler #gbc #sm83 #lr35902


sm83 decoder for the yaxpeax project

2 unstable releases

0.2.0 Jul 7, 2021
0.1.0 Dec 7, 2020

#271 in Emulators

0BSD license

816 lines


decoder for the Sharp SM83 cpu core, which was famously used in the Nintendo Game Boy and Game Boy Color.

some documentation refers to the processor in those devices as the Sharp LR35902 - this is partially correct: the SoC powering the Game Boy and Game Boy Color is branded LR35902, but the cpu contained therein appears to be very much like an SM83 core. gekkio has done significantly more Game Boy reverse engineering than i plan to do in my life, and has a more compelling argument with citations in this nesdev post

this decoder is heavily derived from the opcode tables at pastraiser and in gekkio's technical reference


the sm83 microcomputer, being over two decades old, is not changing much. the initial release of yaxpeax-sm83 will likely be 0.1. a 1.0 release has a short but important worklist:

1.0 checklist

  • compare the opcode table from pastraiser with gekkio's documentation. if there are disagreements, figure out what is correct and add appropriate tests
  • confirm acceptable disassembly of real sm83 programs


~48K SLoC