gameboy-emulator

A pure C (C with class, if you may say) rework of https://github.com/xiongnemo/nekomimi-gameboy-emulator-1 (https://github.com/DarkKowalski/nekomimi-gameboy-emulator)

Status

CPU

• Full CPU Emulation: working.
• Interrupts: working.

Cartridge (MBC)

• ROM switching: working

• External RAM: implemented, but seems not implemented correctly. Exist in the code but not used (Refer to mmu.c).

• MBC Implemented:

  • MBC1 (Address lines may not be correct)
  • MBC2 (Not tested)
  • MBC3
  • MBC5 (Not tested)
  • Rumble Carts

PPU

• PPU (Scanline): working.
• PPU (FIFO): Can't render windows, will fix.

Joypad

• Joypad: working.

RAM

• RAM: working.

APU

• APU exists (callback driven) but the speed is roughly 2 to 6 times as fast as the emulation speed.

Screenshots

CPU Instructions

The Legend of Zelda: Link's Awakening

Kirby's Dream Land (USA)

Kirby's Dream Land 2 (USA)

Super Mario Land 2 - 6 Golden Coins (USA) (Rev-B)

Pokemon Blue (MBC3)

Harvest Moon GB

Development

Prerequisite

• gcc: Some macros is GNU extension.

nemo @ nemo-g15-5511 in ~\Documents\GitHub\gameboy-emulator on git:dev x [00:00:00]
$ gcc --version
gcc.exe (x86_64-posix-seh-rev0, Built by MinGW-Builds project) 15.1.0
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

• SDL3: You should have SDL3 installed or accessible in your system.

To use the provided Makefile, the folder structure (on Windows) should be as follows:

├─reference
│  └─...
├─SDL3
│  ├─bin
│  ├─include
│  │  └─SDL3
│  ├─lib
│  │  ├─cmake
│  │  │  └─SDL3
│  │  └─pkgconfig
│  └─share
│      └─licenses
│          └─SDL3
├─src
└─test

Example configuration for VS Code

• Install C/C++ extension
• Setup SDL3 include path in c_cpp_properties.json

Test

To mention, CPU test does not require SDL3.

All tests

make test > test.log 2>test.err.log

Run specific test

make <cpu|ram|cartridge>-test > test.log 2>test.err.log

Run emulator

make
./dmg <rom_file>

Flags

Usage: ./dmg [options] <rom_file>
Options:
  -h, --help            Display this help message
  -d                    Enable debug output
  -v                    Verbose output (WARN, -v INFO, -vv DEBUG, -vvv TRACE, default: 0)
  -s, --scale <n>       Window scale factor (1-6, default: 2)
  -p, --serial          Enable serial output printing
Examples:
  ./dmg SuperMarioLand.gb
  ./dmg -d -vv zelda.gb
  ./dmg --serial cpu_instr.gb

Keys

W - Up
A - Left
S - Down
D - Right
J - A
K - B
LSHIFT - SELECT
ENTER - START
ESC - Quit
P - Print FPS (lifetime + this frame)
F1 - Screenshot (Default: gameboy_framebuffer.bmp)
LALT - Toggle joypad (enable/disable)
LCTRL - Fast forward

Credits

The Ultimate Game Boy Talk (33c3)

cboy

Blargg's test ROMs and source code

gbops

GBEDG

emudev

gbdev

Reddit comment on POP AF

SDL3

And of course, our original project and Thank you ALL.