Gearlynx

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Gearlynx is a very accurate, cross-platform Atari Lynx emulator written in C++ that runs on Windows, macOS, Linux, BSD and RetroArch, with an embedded MCP server for debugging and tooling.

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 opening an issue.

Downloads

Notes:

Features

  • Very accurate emulation supporting the entire commercial Atari Lynx catalog and most homebrew and demos.
  • User selectable Lynx I or Lynx II emulation.
  • Compressed and homebrew ROM support (lnx, lyx, o, and zip).
  • Save states with preview and rewind support.
  • Run-ahead support to reduce input latency.
  • Very accurate audio emulation with configurable low-pass filter (mimics original Lynx audio hardware).
  • VGM recorder.
  • Internal database for automatic ROM detection and hardware selection if Auto options are selected.
  • Bank switching (BANK1 + AUDIN) and EEPROM.
  • Save files (EEPROM and NVRAM).
  • Supported platforms (standalone): Windows, Linux, BSD and macOS.
  • Supported platforms (libretro): Windows, Linux, macOS, Raspberry Pi, Android, iOS, tvOS, webOS, 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 run-ahead disassembler that can handle self-modifying code, CPU and memory breakpoints, code navigation (goto address, JP JR and JSR double clicking), debug symbols, automatic labels, memory editor, memory search, Suzy and Mikey register viewer, audio channels, UART, cartridge and video inspector.
  • MCP server for AI-assisted debugging with GitHub Copilot, Claude, Codex and similar, exposing tools for execution control, memory inspection, hardware status, rewind and more.
  • Windows, Linux and macOS Portable Mode.
  • Programmable Shader Chain.
  • ROM loading from the command line by adding the ROM path as an argument.
  • ROM loading using drag & drop.
  • Support for modern game controllers through gamecontrollerdb.txt file located in the same directory as the application binary.

Tips

Basic Usage

  • BIOS: Gearlynx requires a BIOS to work. It is possible to load any BIOS but the original with md5 fcd403db69f54290b51035d82f835e7b is recommended.
  • Mouse Cursor: Automatically hides when hovering over the main output window or when Main Menu is disabled.
  • Portable Mode: Create an empty file named portable.ini in the same directory as the application binary to enable portable mode. On macOS, place the file next to the .app bundle.

Debugging Features

  • Docking Windows: In debug mode, you can dock windows together by pressing SHIFT and dragging a window onto another.
  • Multi-viewport: In Windows or macOS, you can enable "multi-viewport" in the debug menu. You must restart the emulator for the change to take effect. Once enabled, you can drag debugger windows outside the main window.
  • Single Instance: You can enable "Single Instance" in the Emulator menu. When enabled, opening a ROM while another instance is running will send the ROM to the running instance instead of starting a new one.
  • Debug Symbols: The emulator automatically tries to load a symbol file when loading a ROM. For example, for path_to_rom_file.rom it tries to load path_to_rom_file.sym, path_to_rom_file.elf, the loaded-file sidecar path_to_rom_file.rom.elf, path_to_rom_file.lbl and path_to_rom_file.noi. You can also load symbol files using the GUI or the CLI. It supports cc65 (VICE label file), lyxass (EQU), mads (lab and hea), llvm-nm, llvm-mos ELF and vicelbl label formats.
  • Sprite Bounding Box: Homebrew and debug builds can draw colored ImGui outlines after Suzy finishes rendering sprites. It can draw all sprites or only SCBs with SPRCOLL bit 7 ($80) set. Real Lynx hardware ignores this bit, but production builds should clear it.
  • Debug Output: Homebrew games can send debug text to the Trace Logger window using unused Mikey registers $FDC0–$FDC4. Enable Debug Output in the Trace Logger Settings menu and make sure the Debug Messages filter is active. See the register protocol below.
Register Write
$FDC0 Send buffer to Trace Logger (write any non-zero value)
$FDC1 Append byte as ASCII character
$FDC2 Append byte as two hex digits
$FDC3 Set string pointer low byte
$FDC4 Set string pointer high byte (writing this triggers the copy)

Command Line Usage

gearlynx [options] [game_file] [symbol_file]

Arguments:
  [game_file]              Game file: accepts ROMs (.lyx, .lnx, .o) or ZIP (.zip)
  [symbol_file]            Optional symbol file for debugging

Options:
  -f, --fullscreen         Start in fullscreen mode
  -w, --windowed           Start in windowed mode with menu visible
      --mcp-stdio          Auto-start MCP server with stdio transport
      --mcp-http           Auto-start MCP server with HTTP transport
      --mcp-router         Enable compact MCP tool routing
      --mcp-http-address A HTTP bind address (default: 127.0.0.1)
      --mcp-http-port N    HTTP port for MCP server (default: 7777)
      --debug-monitor      Start debug monitor TCP server (default port: 6502)
      --debug-monitor-port N Debug monitor port (default: 6502)
      --headless           Run without GUI (requires --mcp-stdio, --mcp-http, or --debug-monitor)
  -v, --version            Display version information
  -h, --help               Display this help message

MCP Server

Gearlynx includes a Model Context Protocol (MCP) server that enables AI-assisted debugging through AI agents like GitHub Copilot, Claude, Codex and similar. The server provides tools for execution control, memory inspection, breakpoints, disassembly, hardware status, rewind and more. STDIO and HTTP transports are supported, with STDIO preferred.

For complete setup instructions and tool documentation, see MCP_README.md.

VS Code Extension

A source-level debugger for VS Code lives in its own repository: BrianPeek/gearlynx-vscode. It drives Gearlynx over the debug-monitor protocol (--debug-monitor). The wire contract is documented in VSCODE_PROTOCOL_README.md.

Agent Skills

Gearlynx provides Agent Skills that teach AI assistants how to effectively use the emulator for specific tasks:

  • gearlynx-debugging — Game debugging, code tracing, breakpoint management, hardware inspection, and reverse engineering.
  • gearlynx-romhacking — Cheat creation, memory searching, ROM data modification, text translation, and game patching.

Install with npx skills add drhelius/gearlynx. See the skills README for details.

Hardware Tests

Gearlynx passes all tests from Atari Lynx Hardware Test ROMs.

Build Instructions

Windows

  • Install Microsoft Visual Studio Community 2026 or later.
  • Download the latest SDL3 VC development libraries from SDL3 Releases (the file named SDL3-devel-x.y.z-VC.zip).
  • Extract the archive and rename the resulting folder (e.g. SDL3-x.y.z) to SDL3.
  • Place the SDL3 folder inside platforms/windows/dependencies/ so that the include path is platforms/windows/dependencies/SDL3/include/SDL3/.
  • Open the Gearlynx Visual Studio solution platforms/windows/Gearlynx.sln and build.

macOS

  • 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 sdl3
cd platforms/macos
make dist

Linux

  • Ubuntu / Debian / Raspberry Pi (Raspbian):

If you are using Ubuntu 25.04 or later, you can install SDL3 directly. Use the following commands to build:

sudo apt install build-essential libsdl3-dev
cd platforms/linux
make

For older Ubuntu versions (22.04, 24.04), you need to build SDL3 from source first. Use the following commands to build both SDL3 and Gearlynx:

sudo apt install build-essential cmake git curl jq pkg-config \
  libx11-dev libxext-dev libxrandr-dev libxcursor-dev libxfixes-dev \
  libxi-dev libxss-dev libxkbcommon-dev libwayland-dev libdecor-0-dev \
  libdrm-dev libgbm-dev libgl1-mesa-dev libegl1-mesa-dev libdbus-1-dev libudev-dev libxtst-dev
SDL3_TAG=$(curl -s https://api.github.com/repos/libsdl-org/SDL/releases/latest | jq -r '.tag_name')
git clone --depth 1 --branch "$SDL3_TAG" https://github.com/libsdl-org/SDL.git /tmp/SDL3
cmake -S /tmp/SDL3 -B /tmp/SDL3/build -DCMAKE_INSTALL_PREFIX=/usr -DSDL_TESTS=OFF -DSDL_EXAMPLES=OFF
cmake --build /tmp/SDL3/build -j$(nproc)
sudo cmake --install /tmp/SDL3/build
cd platforms/linux
make
  • Fedora:
sudo dnf install @development-tools gcc-c++ SDL3-devel
cd platforms/linux
make
  • Arch Linux:
sudo pacman -S base-devel sdl3
cd platforms/linux
make

BSD

  • FreeBSD:
su root -c "pkg install -y git gmake pkgconf sdl3"
cd platforms/bsd
USE_CLANG=1 gmake
  • NetBSD:
su root -c "pkgin install gmake pkgconf SDL3"
cd platforms/bsd
gmake
  • OpenBSD
doas pkg_add gmake sdl3
cd platforms/bsd
LDFLAGS=-L/usr/X11R6/lib/ USE_CLANG=1 gmake

Libretro

  • Ubuntu / Debian / Raspberry Pi (Raspbian):
sudo apt install build-essential
cd platforms/libretro
make
  • Fedora:
sudo dnf install @development-tools gcc-c++
cd platforms/libretro
make

Contributors

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

Contributors

License

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