J1coding
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Nightly and MoonStore builds identify themselves to RetroAchievements as stock PCSX2, so the server allows softcore only. Hardcore has worked on locally built IPAs and nowhere else. Nothing was broken. pcsx2/Host.cpp reads the client version from ra_ua_secret.h behind __has_include and falls back to a stock agent when the macro is absent. That header is gitignored, so it has never existed on a runner. CI now writes it from the IOS_RA_UA_VERSION repository secret, the way the Android job already writes its keystores from NIGHTLY_RELEASE_KS_B64. A missing secret warns and continues, because fork pull requests never receive secrets and a nightly that fails to publish is worse than one without hardcore. A malformed version fails the build instead: RetroAchievements refuses a version it cannot order, and a refused agent is indistinguishable from an unknown one on the client. Only the nightly and pushes to master embed it. Pull request artifacts keep the stock agent, so a test build is not one more public copy of an identity that needs a release to revoke. A second step reads the finished binary and fails unless the exact version is in it, trailing space included, since a stale 1.2.3 is a prefix of a current 1.2.345. Both iOS jobs are continue-on-error, so that failure does not stop the workflow, but it does skip the upload that follows it, and the publish step treats a missing IPA as absent rather than fatal. A softcore build is not shipped. None of this makes the version private. The compiler bakes the finished agent into the binary as a plain literal, so anyone holding a build can read it out. What the gitignored header prevents is a fork inheriting a live identity straight from source.
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.
Thank You
The ARMSX2 team is eternally indebted to the PCSX2 project it is based on. We are so fortunate to build on their 20 years of hardcore development.
About This Fork
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. For more information, visit this page.
Building
Check out our github actions for the latest build recipe