PSXRecomp

Generic static recompiler framework for PlayStation 1: MIPS R3000A to C to native x64.

Background on the original prototype: I Built a PS1 Static Recompiler With No Prior Experience (and Claude Code)

How to use PSXRecomp

PSXRecomp takes a PlayStation disc image and BIOS and creates a recompilation project containing C source and build scripts.

Generate a project with the released CLI

1. Download psxrecomp-cli-windows-x86_64.zip from Releases.
2. Extract the whole zip to a folder. Keep its contents together.
3. Open PowerShell in that folder and run:

.\psxrecomp.exe build `
  --disc "C:\Games\My Game\game.cue" `
  --bios "C:\BIOS\SCPH1001.BIN" `
  --output "C:\Projects\MyGameRecomp"

Use the .cue file when a game has one, and keep its .bin track files beside it. Single-file .bin and .iso images are also accepted.

The output folder contains:

• generated C source for the game and BIOS;
• game.toml, which you can edit for game-specific settings;
• CMakeLists.txt and build scripts; and
• a local copy of the PSXRecomp runtime source needed by the project.

The downloaded CLI is self-contained. You do not need to install Python or build this repository to generate a project.

Build the generated project

Install CMake, Ninja, a C/C++ compiler, and SDL2 development files. Then run:

powershell -ExecutionPolicy Bypass -File "C:\Projects\MyGameRecomp\build.ps1"

The generated project also includes a shell build script for macOS and Linux:

sh /path/to/MyGameRecomp/build.sh

The ready-made CLI release is currently for 64-bit Windows. You can build the CLI from source on another operating system using the instructions below.

The generated project is a practical starting point, not a promise that every game works without game-specific fixes. PSX games can load extra code and use hardware in ways that require additional configuration or development.

Use only disc and BIOS files you obtained legally. PSXRecomp does not include them. Generated game and BIOS source is derived from those files, so do not redistribute it.

Build the CLI from source

You need Git, Python 3, CMake, Ninja, and a C++20 compiler.

git clone --recurse-submodules https://github.com/mstan/psxrecomp.git
cd psxrecomp
python tools/build_cli.py release

The ready-to-use CLI archive is written to dist/. To package debug binaries instead, run python tools/build_cli.py debug.

On Linux/macOS source checkouts, the same development setup can be driven by:

sh tools/setup_dev.sh

That script builds the CLI/recompiler tools and, when BIOS/generated sources are available, the BIOS-only runtime. Game projects should still be generated with psxrecomp build and built from their generated build.sh.

Where the project is headed. Development so far has been breadth-first: stand up as many games as possible and get them into a playable alpha, proving the framework generalizes. That phase has largely delivered — seven titles now run and ship public builds (see Games). The project is now pivoting to a depth / optimization phase: pushing each game toward 100% static coverage, tightening timing accuracy, driving load times toward zero, and hardening the renderer and audio paths. Expect the fleet to get faster and more accurate rather than wider from here.

What It Is

PSXRecomp translates PS1 MIPS binaries into C, then compiles that C as a native executable linked against a PS1 hardware runtime. The v4 architecture recompiles the real SCPH1001.BIN BIOS and runs it as the kernel — that low-level (LLE) recompiled BIOS is the foundation and the correctness oracle. Everything is architected LLE-first: accuracy comes first, and convenience is layered on top, opt-in, never underneath.

Three things sit on that foundation:

• An optional HLE tier. A high-level BIOS layer can be laid over the recompiled kernel to skip the boot sequence and service a few BIOS calls directly — a player-facing convenience and optimization, enabled by default but fully opt-out ([runtime] bios_hle = false). Anything it doesn't implement falls straight through to the recompiled BIOS, so the LLE path stays load-bearing and remains the oracle every accuracy check runs against.
• Capture-and-compile for overlays. PS1 games stream code off the disc at runtime (overlays) that no ahead-of-time recompiler can see. PSXRecomp captures each overlay the moment it loads and recompiles it to native code, cached and reused forever after (static → gcc → tcc backend).
• A general-purpose interpreter — as a transient safety net, not a fixture. Anything not yet native (a freshly streamed overlay, RAM-installed code) runs in a small MIPS interpreter so the machine is always correct. But the interpreter is explicitly meant to be compiled away: the same capture feeds the TCC-backed sharding pipeline, which turns interpreted code into cached native shards in the background. The more a game runs, the less the interpreter is doing — the goal state is an idle interpreter and 100% native execution.

PSXRecomp is a framework. Game-specific projects live in their own repositories and link this one in as a git submodule to build a game binary.

New here? The fastest way in: docs/EXECUTION_MODEL.md (how a game actually runs — static / native-overlay / interpreter), then docs/ARCHITECTURE.md, docs/BUILDING.md, and CONTRIBUTING.md.

Games

Each game is its own repository that pins a framework commit as a submodule and ships its own release with an in-app launcher. All are alpha — playable, not yet fully validated end to end.

Game	Repository	Latest build	Notes
Tomba!	TombaRecomp	releases	Most mature target; widescreen, supersampling, save/load.
Tomba! 2	Tomba2Recomp	releases	Multi-track disc support, selectable 21:9.
Ape Escape	ApeEscapeRecomp	releases	New launcher, widescreen, memory-card save/load.
Mega Man X4	MegaManX4Recomp	releases	Playable; widescreen.
Mega Man X5	MegaManX5Recomp	releases	Early bring-up.
Mega Man X6	MegaManX6Recomp	releases	Playable; stages, controller, save/load.
Tsumu Light	TsumuLightRecomp	releases	Japanese title (SLPS-02253); early bring-up.

Each game repo carries its own build/run instructions, keyboard/controller mappings, and per-game settings. This repository builds the framework and a BIOS-only runtime — see Release Package below.

Philosophy — toward 100% static recompilation

The goal is simple and absolute: a PS1 game should run as native code, not be emulated. Every MIPS instruction the game executes should ideally have been translated to C and compiled ahead of time. No interpreter on the hot path, no HLE shims, no "good enough" approximation of the hardware — the recompiled BIOS is the kernel, and the recompiled game is the game.

PS1 games make that goal hard in one specific way: overlays. Games stream code off the disc into RAM at runtime and execute it, then overwrite it with the next overlay. That code does not exist in the executable at build time, so a pure ahead-of-time recompiler cannot see it. This is the frontier the project is working through, and it is why this is an alpha/beta: today a majority of a supported game runs as statically recompiled native code, but not yet 100%.

How we close the gap, without ever compromising correctness:

1. Static first. The main executable and the BIOS are fully recompiled ahead of time. This is the bulk of execution and it is always native.
2. Capture → compile → cache for overlays. As the game runs, overlays are captured the moment they load. Offline, each is recompiled to a native DLL keyed by its content, cached, and on later runs loaded and dispatched as native code before any fallback. Coverage grows as the game is played: every overlay someone reaches becomes native for everyone after.
3. Interpreter failover — only for code that isn't static yet. A small MIPS interpreter runs runtime-installed code (overlays/dirty RAM) that hasn't been captured-and-compiled. It is a safety net and a coverage feeder, never a substitute for recompiling static code, and never on the BIOS/main-EXE path.
4. Precision over recall. A piece of code we haven't compiled safely falls back to the interpreter and gets captured for next time — under-coverage self-heals. A piece we compile wrong would corrupt the machine, so the system biases hard toward correctness: native code is only dispatched when its source RAM is provably unchanged, and a registration is revoked the instant the RAM it was compiled from is overwritten.

Two honest bounds. The worst case is always performance, never correctness — anything not yet native simply runs interpreted, correctly.

Known corner case — genuinely self-modifying / per-load-relocated code. Some code is rewritten or relocated to different bytes on every load, so it is not static by definition and cannot be recompiled ahead of time into a single correct translation. This code remains interpreted — permanently, as far as the current design is concerned, and that is an accepted, correct outcome (the interpreter runs it faithfully; only speed is lost). It is a narrow corner, not a wall. We may someday aim to cover it — e.g. by detecting the relocation/patch pattern and baking it in at compile time (keyed by relocation parameters), or by compiling at load time — but we make no promise, and the project is fully correct without it.

The aspiration is 100% static coverage — every reachable instruction native, the interpreter idle. The capture-and-recompile loop converges toward it the more a game is played; this branch is where that machinery is being built.

Status

The framework is at alpha: the LLE recompiled BIOS boots and hands off to the game across all seven targets, and each runs as majority-native code with the capture-and-compile pipeline filling overlays as they're reached. The breadth-first push is essentially done; work now is depth and optimization.

Core subsystems, framework-wide:

Subsystem	State
BIOS recompilation (SCPH1001.BIN)	Boots to shell and hands off to game; also the correctness oracle
HLE BIOS tier	Optional boot-skip + service layer over the recompiled BIOS; default on, opt-out
Game EXE recompilation	Title/menus/save-load/gameplay reached across the fleet
Overlay capture → compile → cache	static → gcc → tcc; coverage grows as a game is played
Interpreter failover	Correctness net for not-yet-native code; being compiled away by sharding
CD-ROM / MDEC / XA	FMVs stream and play; XA/CDDA timing stays authentic
Memory cards	Save and load verified on multiple titles
SIO0 controllers	Digital pad + DualShock config; per-game analog/digital selection
GPU	Software + OpenGL + Vulkan backends; widescreen FOV/HUD work per game
SPU	Working; reverb/noise/sweep and exact SPU-IRQ accuracy still being tightened
Interrupts, COP0, timers, GTE	Working; cycle-accuracy foundation is an active depth-phase focus

Per-game maturity varies — see the Games table. None of the titles is declared fully validated end to end; users perform the final playthrough validation on each release.

Open depth-phase fronts: cycle/IRQ-phase timing accuracy, load-time-toward-zero (data sharding), renderer parity between the software/GL/Vulkan backends, and driving overlay coverage the last mile to 100% static.

Running this repository's runtime without a game is useful for BIOS-only memory-card management; to build and play a title, use its game repo from the Games table.

Release Package

This repository's release is BIOS-only — it is the framework runtime, not a game. Use it for BIOS boot and memory-card management; to play a title, grab its release from the Games table.

1. Download PSXRecomp-v*-windows-x64.zip from Releases.
2. Extract it and run PSXRecomp.exe.
3. Select your legally obtained SCPH1001.BIN BIOS when prompted.

The package does not include a PS1 BIOS, game disc image, generated game code, or save data. The selected BIOS path is saved next to the executable as bios.cfg; delete that file to pick a different BIOS later.

The game recomp projects use the same runtime picker contract but ship a Dear ImGui launcher: on first run it prompts for your legally obtained BIOS and game disc image, then lets you configure video, controls, and per-game settings before launching. Keyboard/controller mappings live in each game's repo and launcher, not here.

Setup

Builds natively on Windows (MSVC/MinGW), macOS (Apple Silicon & Intel), and Linux. The BIOS thread scheduler uses host fibers — Win32 Fibers on Windows, ucontext on POSIX (runtime/src/psx_fiber.c) — so the recompiled BIOS's cooperative thread switching (the CD-boot handoff in particular) behaves the same on every platform.

Requirements at a glance (full details, dependency table, and per-platform prerequisites in docs/BUILDING.md):

• A C/C++ toolchain: MSVC or MinGW/MSYS2 (Windows), Apple Clang (macOS), Clang/GCC (Linux). CMake 3.20+; on macOS/Linux also ninja and pkg-config.
• SDL2 (system / bundled).
• A legally obtained SCPH1001.BIN BIOS dump. Not included.
• For game projects, a legally obtained game disc/EXE dump. Not included.

Build the framework (recompiler tool + BIOS-only runtime):

git clone --recurse-submodules https://github.com/mstan/psxrecomp.git && cd psxrecomp

cmake -S recompiler -B recompiler/build -G Ninja -DCMAKE_BUILD_TYPE=Release && cmake --build recompiler/build
cmake -S runtime    -B runtime/build    -G Ninja -DCMAKE_BUILD_TYPE=Release && cmake --build runtime/build --target psx-runtime

On Windows swap -G Ninja for your generator if you prefer (e.g. -G "Unix Makefiles"); always keep an explicit -DCMAKE_BUILD_TYPE so the generated C is optimized. Game projects generate their own generated/<serial>_*.c files and link this runtime through CMake — see docs/BUILDING.md.

Input

Keyboard and Xbox-style controller input work out of the box; the default fullscreen toggle is F11 / Alt+Enter / Cmd+F. Full button maps, controller configuration, and rebinding live in each game's repo and in-app launcher — they're game-facing, not part of the framework. The BIOS-only framework runtime accepts keyboard input for navigating the BIOS shell and memory-card tools.

Architecture

The recompiler emits C functions and dispatch tables for BIOS and game code. The runtime loads the BIOS/game assets into emulated PS1 memory, links the generated C as native code, and simulates hardware through MMIO handlers for GPU, DMA, timers, CD-ROM, MDEC, SIO0, memory cards, SPU, GTE, and interrupt delivery. The recompiled SCPH1001.BIN is the low-level (LLE) kernel and the correctness oracle; an optional HLE tier lays instant boot-skip and a few BIOS services on top, always falling through to the recompiled BIOS.

Code that can't be seen ahead of time (disc-streamed overlays) is captured and compiled to native code the first time it appears (static → gcc → tcc backend), with a small interpreter as the correctness fallback until it is. Full story in docs/EXECUTION_MODEL.md; component-level detail in docs/ARCHITECTURE.md.

See CONTRIBUTING.md and CLAUDE.md for the development rules, and docs/internal/ for the phased plans and deep design notes (PLAN.md, FAITHFUL_TIMING_PLAN.md, …).

Load Times

The runtime models authentic 1× CD-ROM timing by default — the same read and seek delays as real hardware. On top of that faithful baseline, load-time acceleration is opt-in, per game, so the accurate path is never compromised:

• Turbo — a hold-to-fast-forward key that compresses loads on demand.
• [runtime] turbo_loads / idle_skip — automatic acceleration during load waits, with turbo_audio_sink keeping the SPU timeline coherent through the burst.
• Warm CD routes ([[runtime.warm_cd_routes]]) — narrowly-scoped fast read cadence armed on a specific SetLoc, restoring authentic timing the moment the read pattern diverges.

FMV/XA and CDDA streaming, seek, and motor timing always stay authentic regardless of the accelerators. Driving load times toward zero (via data sharding) is an active depth-phase effort — see docs/LOAD_TIME_ZERO.md and docs/disc-speed.md.

Help make your game faster — just by playing it

Why isn't the game already at full speed everywhere? Most of a game's code is converted ("recompiled") into a fast native program ahead of time. But PlayStation games don't keep all of their code on screen at once — they stream extra chunks of code off the disc as you reach new areas (these chunks are called overlays). We can't convert a chunk we've never seen, and the only way to see it is for someone to actually visit that area. Until then, that area's code runs in a slower compatibility mode.

You can help, just by playing. While you play, the game quietly notices which areas are still running in the slow mode, takes a snapshot of them, and converts them to fast native code in the background — often within a minute, while you keep playing. The more places you visit, the faster the game gets. This happens automatically; you don't have to do anything.

Your discoveries persist for you. They are saved in a file written next to the game called overlay_captures.json, and your local cache is rebuilt from it automatically — areas you have visited stay fast on every later session.

Please do not post overlay_captures.json publicly. The file contains verbatim snapshots of the game's code read from your disc, which is copyrighted material — keep it on your own machine, alongside your disc image. A metadata-only contribution format (addresses and checksums, no game code) is planned so discoveries can be shared safely in the future.

Contributing

Contributions are welcome — AI-assisted or not — as long as they're reviewed, tested, and keep the core game-agnostic. A few things hold this project together: the faithful recompiled BIOS is the baseline and oracle, generated code is never hand-edited (fix the recompiler and regenerate), and a change proves itself against the Beetle oracle / on screen rather than by assertion. Game-specific work lives in the game repos, which pin an exact framework commit as a submodule.

Read CONTRIBUTING.md before opening a PR — it covers the core rules, how to verify a change, the regression checklist across the known games, and how a framework fix reaches a game through its pin. Bugs and build problems go to GitHub issues (include gcc -v / OS / generator for build failures); design discussion happens in the R.A.I.D. Discord (invite below).

License

PolyForm Noncommercial 1.0.0. See LICENSE.

The PSX BIOS and game disc images remain copyrighted by their respective owners. This project distributes no BIOS images, no disc images, and no game assets — those are always supplied by the user from their own collection. Release executables (and per-game overlay caches) contain statically recompiled (machine-translated) builds of the original code, the same distribution model used by other static recompilation projects such as N64: Recompiled.

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_{R.A.I.D. — Retro AI Development · a Discord for AI-assisted retro reverse-engineering, decomp & recomp}