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vtlb_Miss raised the exception under the arm64 recompiler and returned, on the assumption that the rec would pick cpuRegs.pc up at the next dispatch. Nothing picks it up: the block runs on and its tail writes its own branch target over the vector PC, while cpuException has already latched Status.EXL. cpuException leaves EPC alone whenever EXL is already set, so from the first swallowed miss onward every exception keeps its predecessor's EPC, and the guest kernel's syscall epilogue erets to an address belonging to the fault. Report the miss and continue instead, as the x86 rec already does. The guest's handler still does not run, so a title that needs demand paging still cannot work under the rec; a stray miss now stays local to the instruction. ee_rec_tlb_divert_tests.cpp describes the divert and stays disabled. With nothing left to set s_recTlbMissOccurred, the poll after every interpreter call goes too. It could not have covered the raise anyway: only the interpreter-call sites had it, so a flag set at an inline access sat there until an unrelated later recCall consumed it and diverted on a pc belonging to neither. This gives up the one case the rec did handle, a miss in a branch delay slot reaching the vector through the cpuRegs.branch bracket epilogue. Its recompiler half moves to the disabled file; the interpreter half stays live, beside a new test pinning the rec's behaviour. The bracket itself stays: the tlb_fallback_* handlers raise from a delay slot on their own.
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