OpenGP

OpenGP

OpenGP is a native PC port of Mario Kart Arcade GP and Mario Kart Arcade GP 2 (Namco, 2005 and 2007, Triforce arcade hardware). It is built by static recompilation, the same approach as Zelda64Recomp and UnleashedRecomp.

The game's PowerPC (Gekko) machine code is translated into C++ ahead of time. That C++ is then compiled together with a runtime that stands in for the Triforce hardware (GameCube GPU, audio DSP, AM-Baseboard, AM-Mediaboard), so the game runs as a normal native program, with modern features such as higher resolutions, widescreen and remappable controls.

How it works

your GGPE02.iso ─extract─> main.dol ─decomp-toolkit─> symbols.txt
                               │                          │
                               └───> gekkorecomp <────────┴── games/mkgp2/recomp.toml
                                         │
                            build/generated/*.cpp   (never committed)
                                         │
                   + runtime/ (C++20) ───┴──> OpenGP executable

Part	Path	What it does
Gekko ISA	common/gekko/	Decoder, disassembler and encoder for every Gekko instruction, including paired singles
Recompiler	tools/gekkorecomp/	Turns a DOL plus a symbol list into C++, one C++ function per guest function
CPU runtime	runtime/ppc/	Register context, guest memory, instruction semantics, interpreter fallback, indirect-call dispatch
Machine	runtime/hw/, runtime/os/, runtime/triforce/, runtime/gx/	Hardware models (interrupts, timers, VI, DSP, AI, SI, EXI, DI), boot and guest threads, the Triforce boards, and the GPU (command processor, vertex loading and transform, textures, EFB copies)
Renderer	runtime/video/	SDL3 GPU renderer: the TEV ubershader, EFB, presenting
Input	runtime/input/	Keyboard, gamepads and wheels (SDL3) mapped onto the cabinet's controls, force feedback, scripted input
App	runtime/app/	Command line, settings, window, the in-game menu (Dear ImGui)
Games	games/	Per-game manifest, symbol maps, recompiler config and patches (mkgp1, mkgp2); what both share in common/ (their main(), SDK replacements, the arcade library's free play and test-menu restart)
Installer	tools/installer/	Builds the games on the player's machine from the installer package: the library the package's launcher uses, and opengp-cli (see docs/packaging.md)
Scripts	tools/*.py, tools/devshell.ps1	Game setup (extract and verify main.dol), naming functions (SDK signatures, the GP 2 decomp, matching functions between the games), Windows build shell
Tests	tests/	Decoder, known-answer semantics and differential tests (interpreter vs recompiled code), and tests of the hardware, renderer front end, settings, input, link, paths, the installer and crash reports

Details are in docs/architecture.md. Notes on the arcade hardware are in docs/triforce.md.

Made with AI

OpenGP is developed with AI. The maintainer decides what gets built and plays the results; most of the code and documentation is written by Claude (Anthropic's model) through Claude Code. Commits made that way end with a Co-Authored-By: Claude line, so the history shows which ones.

The code is held to the same checks as any other:

• The test suite (among others, differential tests that run the same guest code through the interpreter and the recompiled code) runs in CI on every push that changes the code, on Linux, Windows and macOS.
• The hardware follows Dolphin's behaviour, and code ported from Dolphin is marked as such.
• What OpenGP learned from other projects is credited below and in the docs. Nothing is copied from projects that have no license, only facts such as addresses.

TLDR, i check through most commits before committing. i use Claude to commit. so some human commits made by me are also co-authored by Claude.

Playing

Download the launcher package for Windows, Linux or macOS (Apple Silicon) from the releases, unpack it and open OpenGP, the launcher. Add your disc image of each game: OpenGP builds the games on your machine from your images, then plays them (see docs/packaging.md and docs/playing.md). On the command line, opengp-cli builds them the same way.

Building

You need CMake 3.25+, Ninja, Python 3.9+, and GCC 12+ or Clang 16+. On Windows, use clang-cl: the recompiled code relies on weak symbols, which MSVC does not support. Full instructions, including Windows setup, are in docs/building.md.

python3 tools/setup.py           # extracts main.dol from your images in ISO/ (Windows: python)
cmake --preset default           # Windows: . .\tools\devshell.ps1, then --preset clang-cl
cmake --build --preset default
ctest --preset default

Without the game you still get the recompiler, the CPU runtime and the test suite. The tests need no game data: they generate their own PowerPC test programs.

Legal

This repository contains no game code, data or assets, and none may ever be added. That includes the recompiler's output, because it is derived from the game.

To play, you will need your own copy of the game:

• Put your images in ISO/ (or private/). Both folders are gitignored.
• python3 tools/setup.py extracts each game's main.dol into orig/ (also gitignored), and the build reads it from there.
• docs/game-files.md explains how to prepare them.

Mario Kart and Mario Card are trademarks of Nintendo and Namco; Pac-Man and Tamagotchi are trademarks of Bandai Namco; other names belong to their owners. This project is not affiliated with or endorsed by Nintendo, Bandai Namco or Sega.

OpenGP is Copyright (C) 2026 the OpenGP contributors and is licensed under the GPL-3.0-or-later (see LICENSE). Its source code is at https://github.com/OpenGP-dev/OpenGP. Parts of the runtime and tools are ported from the Dolphin emulator (GPL-2.0-or-later) and are marked as such in the source. The third-party code OpenGP and its packages include keeps its own licence: SDL 3 (zlib), Dear ImGui and toml++ (MIT), the boot ROM fonts in thirdparty/gc-fonts (Dolphin's free replacements, based on Droid Sans, Apache-2.0), Qt 6 in the packages' launcher (LGPL-3.0) and others, all listed with their licences in THIRD-PARTY-NOTICES.md.

Releases come with installer packages for Windows, Linux and macOS. 0.1.0 to 1.0.0 were internal releases: they are tags in this repository, with their notes in CHANGELOG.md. 1.0.1 is the first public release.

Acknowledgements

• Dolphin: the reference for Gekko, GameCube and Triforce behaviour, and the source of the runtime's ported parts.
• mkgp2-decomp by naari3: the names of GP 2's functions and globals (and through them GP's), and notes on the games' network code.
• mkgp2-patch by naari3: the Ghidra analysis of GP 2 that the decomp's names grew out of.
• Skip-checks patch by coremaven: where GP 2's hardware checks are, which OpenGP's camera and cabinet-link patches are based on.
• decomp-toolkit: GameCube binary analysis.
• N64Recomp / Zelda64Recomp and XenonRecomp / UnleashedRecomp: the overall design.