Brian Degenhardt
dfef534426
Both desktop resolution pickers ran Native, 2x, 3x ... in whole steps. That is the wrong shape for a handheld at both ends: below native is unreachable even though rendering there is a large win and the GS accepts it -- only the top end is clamped, in GSClampUpscaleMultiplier -- and above native the jump from 1x to 2x is four times the pixels with nothing in between. Both pickers now carry the set the Android UI has offered since issue #207: 0.25x 0.5x 0.75x Native 1.25x 1.5x 1.75x 2x 2.25x 2.5x 2.75x 3x 3.5x 4x 5x 6x 7x 8x Everything above 8x moves behind Extended Upscaling Multipliers, which used to unlock 13x and up. That checkbox was dead on ordinary hardware: the GPU cap is max texture size / 1280, so a 16K-texture part reports exactly 12x and the "supports extended" test wanted more than 12x. It now unlocks anything past 8x, which is the first time it does something on a normal GPU, and 9x-25x still appear only as far as the GPU can actually go. Big Picture indexed two parallel arrays as "slot i means multiplier i+1", which a non-uniform list breaks. Replaced with one table carrying the label, the INI string and the multiplier, filtered against the cap. The quarter steps are all exact in binary, so matching a saved multiplier by equality is safe. Two things fixed in passing, both of which the new list would otherwise have broken. The Qt global tab keyed "nothing found" off index 0 being Native, and index 0 is now 0.25x. And Big Picture passed "1.000000" as its default while the INI is written by StringUtil::ToChars, which produces "1" -- so with no key set the picker read back a value matching no entry and displayed Unknown.
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