<div align="center">

GT4Recomp

Gran Turismo 4, recompiled to run natively on PC.<br> No JIT, no emulator window, full speed.

<br> <img src="docs/images/night-race-hires.webp" alt="Gran Turismo 4 night race at high resolution, 60 FPS" width="100%"> </div>

GT4Recomp is a static recompilation of Gran Turismo 4 (NTSC-U, SCUS-97328) for Windows x86-64. The game's own code is translated ahead of time into C++ and compiled to native machine code; the PS2 hardware it talks to is reproduced in software, and graphics run on Vulkan. Nothing generates code while the game runs.

[!IMPORTANT] You need your own original copy of the game. GT4Recomp does not include or distribute Gran Turismo 4. We only distribute the launcher and the natively recompiled system that runs the game. To play, make a disc image of your own Gran Turismo 4 (USA, v2.00, SCUS-97328) disc as a plain .iso, and for the mod, your own Spec II 1.10 image.

Highlights

• 60 FPS at 100% game speed, with all game code precompiled: the main CPU (EE) and every VU0 and VU1 microprogram run as native code, with no interpreter on the normal path.
• CoreGS 2.0, our own renderer, is the default from 1.3.0: high internal resolutions, sharpening, custom texture packs from the PCSX2 community and a Performance Mode for weaker PCs. GSdx (the PCSX2 GS, in its own process) stays available as the fallback.
• Two games: Gran Turismo 4 v2.00 and Gran Turismo 4 Spec II 1.10 (1.3.0), including images built on Spec II 1.10 such as translations and car packs.
• Native ultrawide and any aspect ratio: 21:9, 32:9, 16:10 or a phone shape; the 3D view widens, the HUD and the race menus keep their 16:9 shape.
• A launcher that sets everything up from your disc image: installer or portable, save library, controller remapping, update channels (Stable and Beta), English and Brazilian Portuguese.
• Any controller through SDL3 (Xbox, DualShock 4, DualSense, Switch Pro...), configurable racing wheels, the full trigger range for throttle and brake, a 360-degree chase camera and camera zoom in races.
• Crash-safe memory card: saves survive a crash or a forced close.

Where we are

Channel	Version	Renderer
Stable	1.2.5	GSdx	The latest final release
Beta	1.3.0-rc14	CoreGS 2.0 (default) · GSdx	Release candidate: Spec II, CoreGS 2.0, new launcher

Choose the channel in the launcher (Settings > General > Channel). Every piece of work is a numbered task in TASKS.md, tested in game before it is released.

Known issues

• Busy driving views on laptop processors (CoreGS 2.0): the player's view with the HUD and the rear-view mirror can drop below 60 FPS on mid-range laptops (the first license, some city tracks). The cause is known (palette changes split the drawing into too many batches) and the fix is planned for the next release candidate.
• Photo mode on slower graphics cards (CoreGS 2.0): frame times can be uneven.
• Some AMD Radeon RX 5000/6000 drivers closed the game while CoreGS 2.0 prepared its shaders. 1.3.0-rc14 guards against it; GSdx works on those PCs.
• Some license demos and menu backgrounds do not play; every license test is playable (why).
• Spec II: only images with Spec II 1.10's game code are supported; earlier Spec II releases are refused.
• Menus, movies and photo mode stay 16:9 (pillarboxed) at other aspect ratios.
• The installer is not code-signed: Windows SmartScreen may warn on the first start ("More info", "Run anyway").
• Most testing was on an AMD graphics card; NVIDIA and Intel cards have had less testing.

Roadmap

Phase	Release	Platform	Renderer	Status
1	1.0.0 - 1.2.5	Windows PC	GSdx (PCSX2 GS, separate process)	Done
2	1.3.0 - 2.0.0	Windows PC	CoreGS 2.0 (our own) as the default · GSdx as the fallback	In progress (1.3.0 beta)
3	after 2.0.0	Linux (native)	CoreGS 2.0	Planned
4	after 2.0.0	Android	CoreGS 2.0 (Vulkan)	Planned

How it works

The EE game code is translated ahead of time into C++ and compiled for x86-64. The VU1 microcode, stored encrypted inside the executable, is recovered and compiled offline and verified against a reference interpreter; the VU0 microprograms are compiled the same way. IOP system services are native, and frames are paced by one high-resolution clock. This is a hybrid recompilation: PS2 hardware is still modelled in software, so we do not claim zero emulation or full PS2 fidelity. Details: Architecture.

Requirements

• Windows 10 or 11, 64-bit, and a processor with SSE4.1 (Intel Core i3/i5/i7, AMD FX or newer).
• A graphics card with Vulkan 1.2 and current drivers for CoreGS 2.0 (GSdx can also use Direct3D 11 on older cards).
• Your own disc image of Gran Turismo 4 USA v2.00 (SCUS-97328), and of Spec II 1.10 for the mod, as a plain .iso. The launcher reads the image where you keep it; it is not copied.

The launcher checks the processor and the graphics card before setup and before Play, and says what is missing.

Install

1. Download the installer (GT4Recomp-Setup-<version>.exe) or the portable zip from Releases: the latest release for Stable, or the newest pre-release for Beta.
2. Start GT4Recomp and choose your disc image. The launcher checks it, prepares the game and its shaders.
3. Press Play.

Updates install from the launcher. Your settings, saves and replays are kept per Windows user in %APPDATA%\GT4Recomp (the portable build keeps them in its own folder). Building from source needs your own game files and a development environment: see the Build guide.

Controls

Controllers work out of the box with the DualShock 2 layout (analog triggers with pressure for throttle and brake) and can be remapped in the launcher (Settings > Controls). The keyboard has a fixed layout:

Key	Action (PS2 button)
W · Enter	Accelerate, confirm (Cross)
S	Brake (Square)
Space	Handbrake (Circle)
A · D · arrow keys	Steer, navigate (D-pad)
Backspace · Esc	Back (Triangle)
Shift	Nitro (R1)
R · F	Gear up · gear down (R2 · L2)
Q	Look back (L1)
C · Tab	Camera (Select)
P	Start / Pause
Alt+Enter, F11	Borderless fullscreen

Support and contributing

• Donate: ko-fi.com/moesuito. Donations pay for the AI development tools behind GT4Recomp.
• Contribute: read CONTRIBUTING.md, then pick a task from TASKS.md or an issue.
• Report bugs: open an issue with the log bundle (Settings > About > Export logs).
• Talk with us: join the GT4Recomp Discord server.

Credits

Contributors on GitHub: Wise (gustavocanepa), the author of gt4-decomp, for the game's function names and a check on GS settings; Julio Vitor Rufino (JulioHeroZ), for racing wheel support, RetroAchievements and the renderer choice kept on updates; Luan Antony (luanantony), for the racing wheel integration, DualSense trigger curves and many fixes and studies. Thank you!

Project	Author	What it gives this project
gt4-staticrecomp, the original project	Kaezzey (Niket Shah)	Where GT4Recomp started: this repository is a fork of his project.
ps2-web-recomp (MIT)	snuri00	The runtime foundation: EE-to-C++ translator, PS2 hardware models and the original VU1 compiler.
gt4-decomp (MIT)	gustavocanepa	GT4's decompilation: function names, class layouts and engine notes (identity).
Nenkai's GT research	Nenkai	File formats and the VU1 microcode encryption scheme (details).
GT4FS	Razer2015	GT4 volume file-system research.
Gran Turismo 4 Spec II	TheAdmiester and contributors	The Spec II mod (the second game). GT4Recomp ships none of its files.
PCSX2 (GPL-3.0)	PCSX2 team	Decades of PS2 knowledge; its GS runs only in the separate gt4-gs.exe.
naga · Vulkan-Headers	gfx-rs · Khronos	Shader compilation at build time · Vulkan API headers.

Gran Turismo 4 Spec II by TheAdmiester and contributors, with credits to Nenkai, ddm, ermaccer, zinklesmesh, pez2k, xfileFIN, Silentwarrior112, Xenn and Submaniac, Silent, Alconautica, hydnhntr, JeyM and pioneerspine; special thanks to DustinEden and the testers and translators listed on the mod's credits page.

Exact revisions and licenses: THIRD_PARTY.md.

License and legal

• GT4Recomp's own code is MIT. The game executable does not contain or link GPL code; the PCSX2 GS (GPL-3.0-or-later) runs only in the separate gt4-gs.exe, built from moesuito/gt4recomp-gs with its source published on each release.
• You bring your own game. The project does not include Gran Turismo 4, Spec II files, disc images, BIOS files, keys or saves; we distribute only the launcher and the recompiled runtime.
• "Gran Turismo" and "PlayStation" are trademarks of Sony Interactive Entertainment. Gran Turismo 4, its logos and artwork belong to Sony Interactive Entertainment and Polyphony Digital. GT4Recomp is an unofficial fan project, not affiliated with or endorsed by either.

Documentation

TASKS · CONTRIBUTING · STATUS · BUILD · ARCHITECTURE · Renderers · Decisions · Journal