Jeen
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The GS software renderer's ARM64 code generators (DrawScanline and SetupPrim) handed the raw RX pointer to their vixl MacroAssembler. On iOS 26+ devices using the LuckTXM JIT mode, executable memory is dual-mapped: a read-execute alias for the CPU and a separate read-write alias for the emitter, offset by g_code_rw_offset. Writing to the RX page faults instantly (KERN_PROTECTION_FAILURE) -- the GS-thread SIGBUS crash seen on iPhone 16 / iOS 27 beta. The EE and VU recompilers already handle this via armGetWritableCodePtr (pcsx2/arm64/AsmHelpers.cpp). Mirror that pattern in the GS path: a file-local gsGetWritableCodePtr() helper adds the offset on real iOS devices and is an identity no-op everywhere else (macOS, iOS Simulator, Android, Legacy-iOS). The original RX pointer is kept as m_code_rx so GetCode() still returns the executable entry point the rasterizer calls into -- vixl's GetStartAddress echoes the constructor argument, so without this override GetCode() would return the non-executable RW pointer. Cross-platform safety: the guard (#if __APPLE__ && TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR) is byte-identical to the already-shipped EE/VU helper. On every non-iOS path the helper returns the pointer unchanged, and g_code_rw_offset is 0, so behaviour is identical to before. The x86 GS path (.all.cpp, selected by CMakeLists.txt:480-490 under ARCH_X86) shares no code with these arm64 files and is not compiled on any arm64 target.
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
- ✅ PS1 games (IOP mode) run at full speed — e.g. Gran Turismo 2 is fully playable
- ✅ 3D games run (if crash try disabling MTVU)
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