ARMSX2

ARMSX2 — Native ARM64 JIT Fork of PCSX2

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, Recompilers and a 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.

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 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.

Interface:OSD now defaults to 65% (was 100%), the stats block was dominating handheld screens. Existing installs still on the old default are migrated once, custom sizes are preserved.Fixed a mislabelled setting. The top slider in On-Screen read "UI Size (borders)" but actually drove the OSD scale, it and the real UI-size slider were sharing one label key. Renamed to "OSD Size" with its own description, and moved UI Size / UI Font Size up beside it so all three sizing controls are together.Added a scroll-to-top button in Settings when scrolling through for example a huge list of cheats (like for GTA SA).

Other:Potential fix for a Vulkan rendering regression on Snapdragon 8 Elite devices, (please let me know). Potential fix for an issue with texture packs not loading correctly and producing garbage data, (please let me know).Improved UI lagging after choosing a skin.Per-game Graphics API, rotation and GPU driver are now per-game instead of global-only. Load state menu slot tiles were squished due to the new Auto-save setting, they're now back to full size and should scale correctly. RetroArch shaders now render at display resolution. CRT scanlines and similar per-pixel effects were being generated at the internal resolution and then upscaled, which made them uneven. They now render at the on-screen size, matching RetroArch.