# ARMSX2 — Native ARM64 JIT Fork of PCSX2
[![All Platforms](https://img.shields.io/github/actions/workflow/status/ARMSX2/ARMSX2/build-all.yml?branch=master&label=All%20Platforms)](https://github.com/ARMSX2/ARMSX2/actions/workflows/build-all.yml)

ARMSX2 is a free and open-source PlayStation 2 (PS2) emulator based on PCSX2. Its purpose is to emulate the PS2's hardware, using a combination of MIPS CPU [Interpreters](<https://en.wikipedia.org/wiki/Interpreter_(computing)>), [Recompilers](https://en.wikipedia.org/wiki/Dynamic_recompilation) and a [Virtual Machine](https://en.wikipedia.org/wiki/Virtual_machine) which manages hardware states and PS2 system memory. This allows you to play PS2 games on your phone, PC, or gaming handheld, with many additional features and benefits.

## Thank You

The ARMSX2 team is eternally indebted to the [PCSX2 project](https://pcsx2.net) it is based on. We are so fortunate to build on their 20 years of hardcore development.

## About This Fork

[![Project Demo](https://img.youtube.com/vi/a1_zydGhVaE/maxresdefault.jpg)](https://www.youtube.com/watch?v=a1_zydGhVaE)

The upstream PCSX2 project ships an ARM64 *interpreter* build for ARM, but its high-performance **JIT recompilers** (EE, IOP, VU0, VU1, and vtlb fast memory) are x86-64 only. 

**This fork exists to close that gap.** The goal is to preserve the correctness features of 20 years of PCSX2 development, while generating the fastest native ARM performance possible.

**Current status:**
- ✅ EE (Emotion Engine) recompiler — integer, float, MMI, COP0/COP1/COP2, branches, load/store
- ✅ IOP (I/O Processor / R3000A) recompiler — full integer, load/store, branches, coprocessors
- ✅ VU (Vector Unit) recompiler — microVU skeleton + Upper FMAC vector ISA complete; Lower ISA and runtime complete
- ✅ vtlb fast memory
- ✅ Native ARM64 binary builds and boots the PS2 BIOS
- ✅ 2D games are already playable
- ✅ 3D games run

### Why LLMs / AI Were Used

A word on methodology:

The x86-64 JIT code in upstream ARMSX2 is **already proven correct** — it has run thousands of PS2 titles for years. The challenge in this port is not emulator design or JIT theory; it is **mechanical translation** of a large, well-understood x86-64 assembly codebase into equivalent ARM64 assembly (via VIXL) while preserving the exact same register-allocation contracts, block lifecycle, and recompiler semantics.

Large language models (LLMs) were used as an **accelerant for this translation work** — pattern-matching x86 JIT boilerplate to ARM64 equivalents, scaffolding emit routines, and keeping the porting velocity high. The JIT *logic* (block compiler, dispatcher, analysis passes, flag pipelines, clamping rules, Tri-Ace hacks, etc.) is taken directly from the upstream x86 implementation and validated against it. **Nothing was hallucinated from scratch.**

In other words: the hard engineering was done by the PCSX2 team over two decades. The hard *typing* — translating ~50k lines of x86 emitter code into ARM64 — is what AI helped compress.

## System Requirements

ARMSX2 targets ARM64 across desktop (macOS, Windows, Linux) and mobile (Android, iOS/iPadOS), all from the single shared core. Our [setup documentation page](https://pcsx2.net/docs/setup/requirements) contains additional details on software and hardware requirements.

Please note that a BIOS dump from a legitimately-owned PS2 console is required to use the emulator. For more information, visit [this page](https://pcsx2.net/docs/setup/bios/).

## Building

Check out our [github actions](https://github.com/ARMSX2/ARMSX2/actions/workflows/build-all.yml) for the latest build recipe