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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 and RetroArch.

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

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

• Windows:
  • Gearsystem-3.7.0-windows-x64.zip
  • Gearsystem-3.7.0-windows-arm64.zip
  • NOTE: If you have errors you may need to install:
    • Microsoft Visual C++ Redistributable
    • OpenGL Compatibility Pack
• macOS:
  • Gearsystem-3.7.0-macos-arm.zip
  • Gearsystem-3.7.0-macos-intel.zip
• Linux:
  • Gearsystem-3.7.0-ubuntu-24.04.zip
  • Gearsystem-3.7.0-ubuntu-22.04.zip
  • Gearsystem-3.7.0-ubuntu-20.04.zip
  • NOTE: You may need to installlibsdl2 andlibglew
• RetroArch:Libretro core documentation.

• 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 andMEMPTR registers.
• Supported cartridges: ROM, ROM + RAM, SEGA, Codemasters, Korean, MSX + Nemesis, Janggun, SG-1000 and many Korean multi-carts.
• Automatic region detection: NTSC-JAP, NTSC-USA, PAL-EUR.
• Accurate VDP emulation, including timing and VDP specifics for SMS, SMS2, GG and TMS9918 modes.
• Support for YM2413 (OPLL) FM sound chip.
• Light Phaser and Paddle Control
• Internal database for rom detection.
• Battery powered RAM save support.
• Save states.
• Compressed rom support (ZIP).
• Game Genie andPro Action Replay cheat support.
• Supported platforms (standalone): Windows, Linux, BSD and macOS.
• 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 LinuxPortable Mode.
• Rom loading from the command line by adding the rom path as an argument.
• Support for modern game controllers throughgamecontrollerdb.txt file located in the same directory as the application binary.

• BIOS: Gearsystem can run with or without a BIOS. You can optionally load a BIOS and enable it. It is possible to run the title included in the BIOS by settingMedia Slot toNone in theEmulator menu. This will emulate a machine without any media plugged in.
• Overscan: For a precise representation of the original image selectOverscanTop+Bottom andAspect RatioStandard (4:3 DAR) in theVideo menu. Game Gear will ignore any overscan settings.
• Mouse Cursor: Automatically hides when hovering main output window or when Main Menu is disabled.
• Portable Mode: Create an empty file namedportable.ini in the same directory as the application binary to enable portable mode.
• Docking windows: In debug mode you can dock windows together by pressing SHIFT and drag'n drop a window into another.
• Debug multi-viewport: In Windows or macOS you can enable "multi-viewport" in debug menu. You must restart the emulator for the change to take effect. Once enabled you can drag debugger windows outside the main window.
• Debug Symbols: The emulator always tries to load a symbol file at the same time a rom is being loaded. For example, forpath_to_rom_file.sms it tries to loadpath_to_rom_file.sym. It is also possible to load a symbol file using the GUI or using the CLI.
• Command Line Usage:gearsystem [rom_file] [symbol_file]

• Install Microsoft Visual Studio Community 2022 or later.
• Open the Gearsystem Visual Studio solutionplatforms/windows/Gearsystem.sln and build.

• Install Xcode and runxcode-select --install in the terminal for the compiler to be available on the command line.
• Run these commands to generate a Macapp bundle:

brew install sdl2cd platforms/macosmake dist

• Ubuntu / Debian / Raspberry Pi (Raspbian):

sudo apt install build-essential libsdl2-dev libglew-dev libgtk-3-devcd platforms/linuxmake

• Fedora:

sudo dnf install @development-tools gcc-c++ SDL2-devel glew-devel gtk3-develcd platforms/linuxmake

• FreeBSD:

su root -c"pkg install -y git gmake pkgconf SDL2 glew lang/gcc gtk3"cd platforms/bsdgmake

• NetBSD:

su root -c"pkgin install gmake pkgconf SDL2 glew lang/gcc gtk3"cd platforms/bsdgmake

• Ubuntu / Debian / Raspberry Pi (Raspbian):

sudo apt install build-essentialcd platforms/libretromake

• Fedora:

sudo dnf install @development-tools gcc-c++cd platforms/libretromake

Zexall Z80 instruction exerciser (from SMS Power!)

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

SMS VDP Test (from SMS Power!)

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

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