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Gearsystem is a very accurate, cross-platform Sega Master System / Game Gear / SG-1000 emulator written in C++ that runs on Windows, macOS, Linux, BSD, iOS, Raspberry Pi and RetroArch.

This is an open source project with its ongoing development made possible thanks to the support by these awesome backers. If you find it useful, please, consider sponsoring.

Don't hesitate to report bugs or ask for new features by openning an issue.


Supported Machines

  • Sega Mark III
  • Sega Master System
  • Sega Game Gear
  • Sega Game 1000 (SG-1000)
  • Othello Multivision


  • Accurate Z80 core, including undocumented opcodes and behavior like R and MEMPTR registers.
  • Supported cartridges: ROM, ROM + RAM, SEGA, Codemasters, Korean, MSX + Nemesis, Janggun, SG-1000.
  • Automatic region detection: NTSC-JAP, NTSC-USA, PAL-EUR.
  • Accurate VDP emulation including timing and Master System 2 only 224 video mode support.
  • Internal database for rom detection.
  • Sound emulation using SDL Audio and Sms_Snd_Emu library.
  • Battery powered RAM save support.
  • Save states.
  • Compressed rom support (ZIP).
  • Game Genie and Pro Action Replay cheat support.
  • Supported platforms (standalone): Windows, Linux, BSD, macOS, Raspberry Pi and iOS.
  • Supported platforms (libretro): Windows, Linux, macOS, Raspberry Pi, Android, iOS, tvOS, PlayStation Vita, PlayStation 3, Nintendo 3DS, Nintendo GameCube, Nintendo Wii, Nintendo WiiU, Nintendo Switch, Emscripten, Classic Mini systems (NES, SNES, C64, ...), OpenDingux, RetroFW and QNX.
  • Full debugger with just-in-time disassembler, cpu breakpoints, memory access breakpoints, code navigation (goto address, JP JR and CALL double clicking), debug symbols, memory editor, IO inspector and VRAM viewer including tiles, sprites, backgrounds and palettes.
  • Windows and Linux Portable Mode by creating a file named portable.ini in the same directory as the application binary.
  • Support for modern game controllers through gamecontrollerdb.txt file located in the same directory as the application binary.

Build Instructions


  • Install Microsoft Visual Studio Community 2019 or later.
  • Open the Gearsystem Visual Studio solution platforms/windows/Gearsystem.sln and build.
  • You may want to use the platforms/windows/Makefile to build the application using MinGW.


  • Install Xcode and run xcode-select --install in the terminal for the compiler to be available on the command line.
  • Run these commands to generate a Mac app bundle:
brew install sdl2
cd platforms/macos
make dist


  • Ubuntu / Debian:
sudo apt-get install build-essential libsdl2-dev libglew-dev
cd platforms/linux
  • Fedora:
sudo dnf install @development-tools gcc-c++ SDL2-devel glew-devel
cd platforms/linux


  • NetBSD:
su root -c "pkgin install gmake pkgconf SDL2 glew"
cd platforms/bsd


  • Install latest Xcode for macOS.
  • Build the project platforms/ios/Gearsystem.xcodeproj.
  • Run it on real hardware using your iOS developer certificate. Make sure it builds on Release for better performance.


  • Ubuntu / Debian:
sudo apt-get install build-essential
cd platforms/libretro
  • Fedora:
sudo dnf install @development-tools gcc-c++
cd platforms/libretro

Raspberry Pi 4 - Raspbian (Desktop)

sudo apt install build-essential libsdl2-dev libglew-dev
cd platforms/raspberrypi4

Raspberry Pi 2 & 3 - Raspbian (CLI)

  • Install and configure SDL 2 for development:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install build-essential libfreeimage-dev libopenal-dev libpango1.0-dev libsndfile-dev libudev-dev libasound2-dev libjpeg-dev libtiff5-dev libwebp-dev automake
cd ~
tar zxvf SDL2-2.0.12.tar.gz
cd SDL2-2.0.12 && mkdir build && cd build
../configure --disable-pulseaudio --disable-esd --disable-video-mir --disable-video-wayland --disable-video-x11 --disable-video-opengl --host=armv7l-raspberry-linux-gnueabihf
make -j 4
sudo make install
  • Install libconfig library dependencies for development: sudo apt-get install libconfig++-dev
  • Use make -j 4 in the platforms/raspberrypi3/x64/ folder to build the project.
  • Use export SDL_AUDIODRIVER=ALSA before running the emulator for the best performance.
  • Gearsystem generates a gearsystem.cfg configuration file where you can customize keyboard and gamepads. Key codes are from SDL.

Accuracy Tests

Zexall Z80 instruction exerciser (from SMS Power!)

Gearsystem passes all tests in Zexall, including undocumented instructions and behaviours.


SMS VDP Test (from SMS Power!)

vdptest.smsvdptest.sms vdptest.sms


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Thank you to all the people who have already contributed to Gearsystem!



Gearsystem is licensed under the GNU General Public License v3.0 License, see LICENSE for more information.