Brian Degenhardt
112bc73c4c
Wires MemoryCardBackup into the app. The snapshot is taken immediately before the emulation thread starts, in MainActivityRuntime.start() and startBios(). At that instant the card file is not open, so the copy cannot catch a half-finished write and there is no thread timing to reason about. It also means the copy holds the card as it stood when the player last finished successfully -- if this session is the one that breaks things, the snapshot is clean by construction. Restoring then loses the current session's saves, which is the trade a save-state slot already makes. The BIOS boot gets one too: its memory card manager can format a card or delete saves off it, so that session is worth a copy for the same reason a game is. Launch also checks the cards it is about to mount. If one will not read AND a verified backup exists, the boot is HELD and the prompt offers to put it back before the game starts. That ordering is not cosmetic: once the console has mounted a card it caches its own picture of the directory in guest memory, and a restore underneath would be written straight over. "Start anyway" stays available -- some people will want to format fresh -- and is remembered only for the launch it was answered for. The memory card screen gets a per-card Backups panel: the snapshots with their date, size and the game that was running, a verified-or-suspect badge, restore, back up now, and the automatic-backups switch. That manual path is the one that actually matters, because the automatic offer cannot fire for the failure players hit most -- a card that verifies perfectly while the save inside it is damaged. Recognising that would mean understanding each game's save format. Restore is refused while a game is running, for the cache reason above, and says so rather than failing quietly. A suspect snapshot is listed rather than hidden: the pre-restore copy of a broken card is exactly what someone may need back.
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