Nintendo Game Boy (DMG & GBC)

Edit on Github | Updated: 1st August 2021

Game Boy Basics

Interested in learning more about the the original Game Boy or Game Boy Color? Excellent! This section will guide you through the basics, starting from basic assembly language all the way to reverse engineering your first game!

Original GameBoy Dot Matrix Game (DMG) Specs

Main specs of the original GameBoy:

  • CPU: z80 - LR35902 (Opcodes: http://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html)
  • RAM: 8KB (32KB in Color)

Game Boy Exclusive Games (DMG & Color)

When it comes to finding a game to reverse engineer, it can be helpful to look at games that are cross-platform to compare builds. But the most valuable reverse engineering projects tend to be the platform exclusives, as these are the games people can no longer play on modern consoles.

List of Original DMG Game Boy exclusives

Wikipedia has compiled an excellent list of games that have never been re-released and thus need a Game Boy to be able to play

List of Game Boy Color exclusives

Wikipedia has compiled an excellent list of games that have never been re-released and thus need a Game Boy Color to be able to play

The Ultimate Gameboy Talk (hardware specs etc)

The 8-bit Game Boy was sold between 1989 and 2003, but its architecture more closely resembles machines from the early 1980s, like the Commodore 64 or the NES.

This talk attempts to communicate “everything about the Game Boy” to the listener, including its internals and quirks, as well as the tricks that have been used by games and modern demos, reviving once more the spirit of times when programmers counted clock cycles and hardware limitations were seen as a challenge.


Game Boy Technology

Game Boy Assembly Language (Z80-like)

The Game Boy has a variant of the Zilog Z80 processor, well technically it is a CPU between the i8080 and the Z80, it is not binary compatible with either but there are similarities. You need a assembler that can handle the Game Boy specific opcodes in order to write functional code for the Game Boy in assembly language.

gbZ80 Assembly programming for the Gameboy and Gameboy Color

ChibiAkumas has an excellent page with tutorials and information to get started with Game Boy assembly language

Game Boy Boot ROM (Bootstrapping)

Every game produced for the Game Boy required a little piece of code known as the “bootloader” or boot code to initialise the state of the console. You don’t have to know anything about this, but it can be fascinating to find out what the Game Boy does as soon as you hit that power button.

A Look At The Game Boy Bootstrap: Let The Fun Begin!

RealBoy has an excellent page that gives you an in-depth look at how the Game Boy's bootloader works


Reverse Engineering Game Boy Games

There have been a few very successful reverse engineering projects for the Game Boy, one of the most successful is the Pokemon dissassembly which managed to reverse engineer the entire game into a rebuildable ROM!

Pokemon Red/Blue/Yellow

The Pokemon Reverse Engineering Team (PRET) have managed to pull off a marvellous achievement, they have fully reverse engineered Pokemon Red and Blue back into retail-matching assembly code.

Reversing Pokemon Red and Blue (Game Boy)

For more information about the project check out this post.

In August 2016 the website KZone started a full disassembly of the classic Game Boy game Link’s Awakening, along the way they have written some excellent in-depth articles about how the game works. Check it out!

Disassembling Link’s Awakening

Find out how Zelda Link's Awakening for Game Boy works at KZone!

Looney Tunes: Carrot Crazy

Reverse Engineering Carrot Crazy

Find out how to reverse engineer Looney Tunes: Carrot Crazy for the GBC

Crystalis


Game Boy Development

Game Boy Development Kit Hardware

Special hardware was sold directly from Nintendo in order to make it easy for third party developers to get started making their own games for the new handheld.

Gameboy (DMG & GBC) Development Kit Hardware

For more information about the development hardware used for Game Boy projects check out this post.

Game Boy Software Development Kit

Along with the hardware, Nintendo also provided a fairly limited software development kit, which contained tools such as z80 assemblers and linkers.

Game Boy Software Development Kits

For more information about the SDK used to make Game Boy games check out this post.


Game Boy Hardware

Hardware Architecture

We used to have a post on the hardware architecture of the Game Boy, but now we have replaced it for a link to the far superior page on copetti.org, it is a must read for any reverse engineer or beginner emulator developer.

Game boy Architecture - A Practical Analysis

This page on copetti.org has everything you need to know about the Game Boy Hardware, it is a must read!

Game Boy Pocket Hardware Schematics

If you want to go really low level into the Game Boy hardware, you can view a re-creation of the Gameboy Circuit Schematics over on Github: gb-schematics/MGB-xCPU.pdf at master · Gekkio/gb-schematics · GitHub

The Game Boy, a hardware autopsy


Super GameBoy


GB Booster

Similar to the Super GameBoy but this is for the Nintendo 64 and not licenced by Nintendo, I first saw this for sale in issue X of the UK Nintendo Official Magazine.

For more information:

  • http://www.chrismcovell.com/gbbooster.html
  • https://gamehacking.org/wiki/Game_Booster_(Nintendo_64)

Wide Boy 64

Official device to play gameboy (including gba) games on the N64, but was not sold to the general public. You had to be a game developer or press in order to buy one from Intelligent Systems.


Datel Game Booster for Sony Playstation

Similar to the Super GameBoy but this is for the Sony Playstation!


GameBoy Printer


Source Code

Mr Do! For Original Game Boy

The source code for the Game Boy classic Mr Do! has been kindly released by two of the original game developers and can provide an excellent reference for how retail Game Boy games were developed in 1990!

Mr Do! Source Code (Game Boy)

For more information about the source code check out this post.


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