RustySNES

Precise. Pure. Powerful.

Overview

RustySNES is a cycle-accurate Super Nintendo Entertainment System (SNES) emulator written in pure Rust. Following the lineage of its predecessor RustyNES, it targets the Mesen2 / higan / ares accuracy bar — a master-clock lockstep scheduler, a strictly-owned bus, and a deterministic audio resync model.

Beyond reference accuracy, RustySNES is a real, playable emulation platform today: a native desktop shell (winit + wgpu + cpal + egui) boots real commercial ROMs with picture, sound, and control, alongside 11 cartridge coprocessors, save states with a thumbnail 10-slot manager, rewind, run-ahead, a Lua 5.4 scripting/TAS engine, Game Genie / Pro Action Replay cheats, GGPO-style rollback netplay, RetroAchievements, a growing multi-panel debugger, and a live in-browser WebAssembly build. See to-dos/VERSION-PLAN.md for the named, versioned release ladder from v1.0.0 "Zenith" (the production cut) onward.

Try it in your browser — no install required.

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Why RustySNES?

RustySNES combines accuracy-first emulation with the safety guarantees of Rust, and is building toward the same modern-feature breadth as its sibling project RustyNES, tracked in lockstep (to-dos/LOCKSTEP-CHECKLIST.md) rather than a one-time snapshot.

Key differentiators:

• Reference-grade accuracy — a from-scratch core on a 21.477 MHz NTSC master clock with a lockstep scheduler for every chip. The 5A22 CPU's variable-cycle (6/8/12) instruction timings and dot-accurate PPU/HDMA behavior are cycle-exact, not approximated: the 65C816 and SPC700 both clear their per-opcode SingleStepTests oracles at 0-diff.
• Determinism as a hard contract — the asynchronous SPC700/S-DSP audio processor is kept perfectly coherent with the main CPU through an integer relative-time accumulator, with no floating point in the timing path. The same seed, ROM, and input sequence yield a bit-identical framebuffer and audio output — the foundation save states, rewind, run-ahead, and rollback netplay all build on.
• Honest accuracy tiering — every coprocessor/board is tiered Core / Curated / BestEffort (see docs/adr/0003); a CI honesty gate ensures no unverified BestEffort board ever backs the accuracy oracle. Nothing is silently degraded, and every known gap (a coprocessor boot issue, an unwired peripheral, an incomplete opt-in feature) is documented in docs/accuracy-ledger.md rather than hidden.
• A CI safety net that actually gates merges — cargo test --workspace and the full clippy matrix now run on every pull request that touches code (previously only on a tagged release), behind a single required ci-success check; the no_std build, the 3-OS test matrix, and the bench regression gate run on every push to main, every release tag, and a weekly cron (docs/adr/0011). A pure-docs PR (like this one) skips the code-only jobs entirely rather than spending CI minutes proving nothing changed.
• Safe, modular Rust — the chip stack is no_std + alloc with a one-directional workspace graph, making each component independently testable, fuzzable, and benchmarkable.

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Feature highlights

Feature	Description
Cycle-Accurate Core	65C816 + SPC700 both 0-diff vs. their SingleStepTests per-opcode oracles; a master-clock lockstep scheduler; dot-accurate PPU/HDMA/interrupts
11 Coprocessors	DSP-1, Super FX/GSU, SA-1 (Core/Curated, oracle-gated); DSP-2/4, ST010, CX4, OBC1, S-DD1 (BestEffort, real-title validated); ST018, S-RTC (BestEffort, unit-tested); SPC7110 (implemented — the local dump is a ROM-sourcing gap, not an open bug)
Native Desktop Frontend	winit + wgpu + cpal + egui; keyboard + gamepad input, drag-and-drop/zip-archived ROM loading, automatic coprocessor-firmware + .srm SRAM loading
WebAssembly Build	The SAME App/egui shell as native (wasm-winit), deployed live at the hosted demo, plus a lighter canvas-2D fallback (wasm-canvas), a PWA/offline service worker, and a <5 MiB gzip size-budget CI gate
Save States	A quick-save slot plus a disk-backed, thumbnail-previewed 10-slot manager, keyed per-ROM by SHA-256, on a versioned deterministic snapshot envelope
Rewind / Run-Ahead	A bounded ring buffer of full snapshots + an N-frame peek-and-discard run-ahead, both config-driven and off by default
Peripherals	Mouse / Super Scope / Super Multitap — the real 2-bit-per-clock serial-shift-register protocol, ported from ares, not a stub
Lua Scripting + TAS	A sandboxed Lua 5.4 (mlua) engine with full-bus reads / WRAM writes + per-frame callbacks, and a deterministic TAS movie record/playback format
Cheats	Game Genie / Pro Action Replay codes, applied as a Bus read intercept (not a WRAM poke, since real codes target cartridge ROM)
Rollback Netplay	GGPO-style 2-player rollback over native UDP, proven bit-identical resimulation under adverse network conditions; a WebRTC transport exists at the crate level
RetroAchievements	A native FFI bridge around the vendored rcheevos rc_client C API — login, achievements, and unlock toasts
Desktop UX Shell	Light/dark/system themes, 25%-300% speed presets, fullscreen, a key-rebind grid, a Performance panel (FPS/frame-time/audio-health + a rolling sparkline), and a first-run welcome modal
CRT / HQx Post-Filters	A presentation-only post-filter pipeline (scanlines + aperture mask, an HQ2x-style edge-directed blend); the no-filter default stays byte-for-byte identical to the pre-filter blit
HD Texture Packs	A pack.toml loader + pure-Rust PNG decoder + CPU compositor, wired into the live wgpu present path at a fixed 2x upscale (hd-pack, off by default)
7-Panel Debugger	CPU / PPU / APU / Cart / Watch / Memory-Compare / Docs panels behind debug-hooks, extracted into a dedicated debugger/ module — read/write watchpoints, a 65C816 disassembler + PC breakpoints/step controls, a live hex memory window, and an in-app glossary
Libretro Core	A real rustysnes-libretro core loadable by RetroArch — region-aware NTSC/PAL, cheats, coprocessor-firmware auto-resolution, peripheral negotiation, raw memory-map pointers
Documentation Site	A Material-for-MkDocs handbook at /docs/, alongside the playable demo (/) and rustdoc (/api/) on GitHub Pages
Pure Rust	no_std + alloc chip stack; a one-directional crate graph so each chip is independently fuzzable/benchmarkable

Legend for the accuracy tiers: Core/Curated = cross-checked against an independent reference oracle; BestEffort, real-title validated = boots a real commercial title to gameplay content; BestEffort, unit-tested = no commercial dump in the local corpus yet. See docs/STATUS.md for the always-current per-subsystem detail, docs/accuracy-ledger.md for the disposition of every named residual, and to-dos/VERSION-PLAN.md for exactly which release each remaining item lands in.

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Showcase

A cross-section of the commercial library running pixel-accurately on RustySNES — Super Mario World, The Legend of Zelda: A Link to the Past, Super Metroid, and Chrono Trigger on the base LoROM/HiROM path; Donkey Kong Country's pre-rendered ACM art; Super Mario Kart on the DSP-1 math coprocessor; Star Fox's Corneria intro rendered live by the Super FX/GSU core; and Kirby Super Star on SA-1.

The full per-coprocessor visual corpus lives in screenshots/external/commercial/ — boot / title / gameplay frames spanning every LoROM/HiROM × coprocessor combination in the local ROM corpus, generated by scripts/screenshots/generate.sh (see screenshots/README.md).

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Features

Emulation core

• Master-clock-precise scheduler. A 21.477 MHz NTSC master clock drives the CPU, PPU, and APU in lockstep — every chip advances off the same tick count, so mid-instruction PPU/HDMA events (a mid-scanline scroll write, an HDMA-driven register update visible only starting the following line) work without per-quirk patches.
• Cycle-accurate WDC 65C816 (Ricoh 5A22) — all opcodes and addressing modes, native and emulation mode, variable 6/8/12-cycle bus access timing, REP/SEP/XCE, and cycle-exact interrupt/DMA timing — 0-diff (state + cycles) against the SingleStepTests/65816 oracle (5,119,999 / 5,120,000; the one residual is a documented inter-reference divergence, not a bug — docs/adr/0002).
• Cycle-accurate PPU1 (5C77) + PPU2 (5C78) — BG modes 0-7, Mode 7 affine transforms, the full 128-sprite OAM pipeline, color math, windows, and a per-scanline compositor that renders each line one dot before that line's own HDMA can mutate the registers it reads, matching real hardware's mid-scanline register-visibility timing.
• Cycle-accurate SPC700 + S-DSP — the SMP advances in cycle-exact sub-instruction lockstep with the main CPU via an integer relative-time accumulator (no floating point in the timing path), and the S-DSP is itself cycle-stepped (32 ticks per 32 kHz sample) so a mid-instruction DSP-register read sees cycle-correct envelope state. 0-diff against the SingleStepTests/spc700 oracle (256,000 / 256,000) and a literal PASSED TESTS verdict on all four blargg spc_* ROMs.

Cartridges and coprocessors

• LoROM / HiROM / ExHiROM memory-map decode with score-based header detection, plus an unofficial ExLoROM decode path (bsnes-sourced, no real-ROM validation yet).
• 11 cartridge coprocessors — one board/family per row of docs/STATUS.md's coprocessor tier matrix (DSP-2 and DSP-4 share one row and one count, as do ST010 and ST011), each honestly tiered (Core / Curated / BestEffort — docs/adr/0003):
  • Core/Curated (oracle-gated): DSP-1/1A/1B (a full µPD7725 LLE engine, shared by six DSP variants), Super FX / GSU-1/2 (a full Argonaut RISC core), SA-1 (a real second 65C816 instantiated and stepped in lockstep with the main CPU).
  • BestEffort, real-title validated: DSP-2/4 (the shared DSP LLE engine retargeted per variant — validated against real Dungeon Master and Top Gear 3000 respectively), ST010 (the same shared engine, validated against real F1 ROC II; ST011 shares the row but has no confirmed real-title detection entry yet), S-DD1 (a Golomb-code decompressor streamed during DMA), CX4 (a clean-room HG51B169 core), and OBC1.
  • BestEffort, unit-tested: ST018 (a full ARMv3 core), S-RTC — no commercial dump in the local corpus yet.
  • SPC7110 is fully implemented (DCU/ALU/data-port + a paired Epson RTC-4513), but the one locally available dump turned out to be a fan-translation ROM hack, not an original cartridge — a documented ROM-sourcing gap, not an open bug (docs/rom-test-corpus.md).
• See docs/cart.md for the full coprocessor implementation detail and docs/STATUS.md for the always-current per-suite pass counts.

Modern features

• RetroAchievements (opt-in retroachievements feature, native-only) — a native FFI bridge around the vendored rcheevos rc_client C API: login, achievements, and unlock toasts.
• Rollback netplay (opt-in netplay feature) — GGPO-style 2-player rollback over native UDP, proven bit-identical resimulation under adverse network conditions (latency, jitter, packet loss); a WebRTC transport exists at the crate level.
• Lua 5.4 scripting + TAS (opt-in scripting feature, native-only) — a sandboxed mlua engine (io/os/require/debug denied, a runaway-loop instruction budget) reads the full 24-bit bus and writes WRAM through emu.read/emu.write, plus per-frame callbacks; a deterministic rustysnes_core::movie TAS format records/replays input logs bit-identically against a committed ROM. See docs/frontend.md §Scripting.
• Cheats (opt-in cheats feature) — Game Genie and Pro Action Replay code decoding, applied as a Bus read intercept rather than a WRAM poke, since real codes overwhelmingly target cartridge ROM.
• Save states, rewind, and run-ahead — a quick-save slot plus a disk-backed, thumbnail-previewed 10-slot manager on a versioned deterministic snapshot envelope (docs/adr/0006); a bounded rewind ring buffer and an N-frame run-ahead, both config-driven and off by default.
• CRT / HQx post-filters — a presentation-only pipeline (Settings → Video / View → Post-filter): scanlines + an aperture mask, and an HQ2x-style edge-directed upscale blend. The no-filter default (PostFilter::None) stays byte-for-byte identical to the pre-filter direct blit.
• HD texture packs (opt-in hd-pack feature, off by default) — a palette-inclusive allocation-free tile-identity hash computed in rustysnes-ppu, a pack.toml loader + pure-Rust PNG decoder, and a CPU compositor wired into the live wgpu present path at a fixed 2x upscale. See docs/adr/0010.
• Peripherals — Mouse, Super Scope, and Super Multitap, implemented as the real 2-bit-per-clock serial-shift-register protocol (ported from ares), including WRIO IOBIT plumbing and the Super Scope's PPU H/V-counter beam latch — not stubs.
• Libretro core — rustysnes-libretro wraps the same deterministic core as a RetroArch-loadable shared library: region-aware NTSC/PAL geometry + timing, cheat support, coprocessor-firmware auto-resolution, Mouse/Super Scope/Multitap peripheral negotiation, and raw WRAM/VRAM/SRAM memory-map pointers. See docs/libretro.md.

Debugger and tooling (debug-hooks, extracted v1.7.0-v1.8.0)

The debugger overlay was extracted from an inline block in ui_shell.rs into its own debugger/ module (v1.7.0 "Telemetry") and deepened with a second rung of panels (v1.8.0 "Tracepoint"), all read-only and determinism-preserving:

• CPU / PPU / APU / Cart panels — live register state, a 65C816 disassembler with PC breakpoints and step controls, per-scanline PPU state, and per-voice S-DSP state.
• Watch panel — read/write watchpoints plus a live 512-byte hex memory window (via Bus::peek, the same non-intrusive read the disassembler uses; I/O register space reads back as 00 rather than a live register value, since Bus::peek deliberately doesn't model registers).
• Memory Compare panel (v1.8.0) — captures a baseline of the Memory panel's current window and diffs it against the live window every frame, showing only the rows that changed.
• Docs panel (v1.8.0) — an in-app SNES-terminology glossary (docs/glossary.md, embedded at compile time) plus a link to the full MkDocs handbook.

Write-capable hex editing, RAM search, a call-stack view, an instruction/event trace buffer, an inline 65816 assembler, and per-coprocessor-type register panels are honestly scoped as follow-up work, not silently dropped — see CHANGELOG.md's v1.7.0/v1.8.0 entries and to-dos/VERSION-PLAN.md.

CI, docs, and web (v1.5.0-v1.6.0)

• A CI safety net that actually gates merges (v1.5.0 "Bedrock") — cargo test --workspace now runs on every PR (a test-light job), not just tagged releases; a changes/setup job pair computes a light-vs-full run mode per push, and the full clippy matrix / no_std build / bench gate now also run on every push to main, plus a weekly drift-net cron. A single ci-success job is the required branch-protection check. See docs/adr/0011.
• Documentation site + PWA (v1.6.0 "Lighthouse") — a Material-for-MkDocs handbook at /docs/, alongside the wasm demo (/) and rustdoc (/api/), served by a single web.yml workflow that also enforces the <5 MiB gzip wasm size budget on every PR. The wasm demo gained PWA/offline support (a web manifest, a stale-while-revalidate service worker).
• docs/accuracy-ledger.md (v1.6.0) — every known approximation or divergence mapped to an explicit disposition (Remediated / No-stricter-oracle-available / Deferred / Out-of-scope), the "why" companion to docs/STATUS.md's pass-count dashboard.

_{The Amazing Spider-Man: Lethal Foes — multi-layer BG parallax, sprite compositing, and HUD overlay, all dot-accurate output straight from the cycle-accurate PPU pipeline every title runs through.}

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Crates & Architecture

The workspace strictly enforces a one-directional dependency graph to isolate emulation systems from one another, connected only through the core bus.

Crate	Role
rustysnes-cpu	WDC 65C816 (Ricoh 5A22)
rustysnes-ppu	PPU1 (5C77) + PPU2 (5C78)
rustysnes-apu	SPC700 + S-DSP
rustysnes-cart	LoROM/HiROM/ExHiROM + all 11 coprocessor implementations
rustysnes-core	The Bus + master-clock scheduler tie crate, including peripherals (mouse/scope/multitap)
rustysnes-savestate	The versioned save-state envelope shared by every board + chip
rustysnes-frontend	The winit + wgpu + cpal + egui desktop/web shell (binary rustysnes), including the debugger/ module
rustysnes-netplay	GGPO-style rollback netcode (native UDP + a WebRTC transport)
rustysnes-cheevos	RetroAchievements rcheevos FFI bridge (opt-in, native-only)
rustysnes-script	Sandboxed Lua 5.4 scripting engine + TAS movie format (opt-in, native-only)
rustysnes-libretro	Native Libretro API core wrapper (RetroArch)
rustysnes-test-harness	The accuracy oracle (SingleStepTests runners, golden-log suites, per-coprocessor commercial-ROM validation, boot-screenshot generation)

Three load-bearing architectural decisions, detailed in docs/architecture.md:

1. A shared master-clock timebase. Every chip advances off the same 21.477 MHz master clock in lockstep, so mid-instruction PPU/HDMA events work without per-quirk patches.
2. The Bus owns everything mutable. rustysnes-core::Bus holds the PPU, APU, cart, and controller state; the CPU borrows &mut Bus during execution.
3. A one-directional workspace graph. No chip crate depends on another; rustysnes-core ties them together, so each chip is independently fuzzable and benchmarkable.

See docs/DOCUMENTATION_INDEX.md for the full documentation map (subsystem specs, ADRs, testing strategy, and more).

Project layout

crates/        Cargo workspace: the crates above
docs/          Implementation specs, ADRs, the MkDocs handbook source, and STATUS.md
                (single source of truth)
ref-docs/      Immutable deep-research SNES hardware reference
ref-proj/      Study clones of reference emulators (gitignored; bsnes/ares/Mesen2)
tests/roms/    Committed permissive corpus + gitignored external/ (commercial dumps +
                coprocessor firmware — never committed, ADR 0003)
screenshots/   Committed boot-screenshot corpus + curated showcase/montage images
scripts/       Screenshot generation, wasm size-budget gate, bench regression check
to-dos/        The roadmap (ROADMAP.md) and the named, versioned release ladder
                (VERSION-PLAN.md)

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Quick Start

Build from source

Prerequisites:

• Rust 1.96 — pinned via rust-toolchain.toml and auto-installed by rustup.
• Linux desktop dependencies for winit / wgpu / cpal / egui (see below).
• Git.

# Clone the repository
git clone https://github.com/doublegate/RustySNES.git
cd RustySNES

# Build the workspace (release)
cargo build --release --workspace

# Run a ROM you legally own
cargo run --release -p rustysnes-frontend -- path/to/rom.sfc

# Optional: build with one feature (e.g. RetroAchievements)
cargo run --release -p rustysnes-frontend --features retroachievements -- path/to/rom.sfc

# Maximal NATIVE build — every opt-in feature at once (debug-hooks, scripting,
# cheats, netplay, retroachievements, hd-pack). Aliases make it a one-liner:
cargo full-run path/to/rom.sfc   # run the most fully-featured desktop binary
cargo full-build                 # build it (= --release -p rustysnes-frontend --features full)

The full build is purely additive — the default/shipped build and the emulation core are unchanged. emu-thread (a dedicated emulation thread) is deliberately excluded from full: it isn't feature-complete yet (movies, Lua scripting, RetroAchievements, and rewind-recording remain unported — see docs/frontend.md).

The frontend opens a window (scaled, aspect-correct), starts audio via the OS default device, and runs the ROM. With no ROM path, it opens straight to the menu shell (File → Open ROM…).

Command-line help

The native binary ships a clap 4 CLI with styled --help, a help subcommand, shell completions, and (on a terminal) an interactive help browser:

rustysnes --help                 # styled usage + examples + keyboard summary
rustysnes help                   # browse all topics (interactive TUI on a terminal)
rustysnes help coprocessors      # one topic, printed (also works piped: `… | less`)
rustysnes completions fish       # print a shell-completion script

Help topics: controls, hotkeys, gamepad, features, coprocessors, config, scripting, netplay, about. The interactive browser is behind the default-on help-tui cargo feature; piped/non-terminal output falls back to a static page.

Platform-specific dependencies

Ubuntu / Debian:

sudo apt-get install -y libxkbcommon-dev libwayland-dev libxkbcommon-x11-dev libasound2-dev libudev-dev

CachyOS / Arch:

sudo pacman -S --needed libxkbcommon wayland alsa-lib systemd-libs

macOS / Windows: no extra system dependencies are required for the default build. The optional retroachievements and scripting features additionally need a C compiler for their vendored C sources (rcheevos, mlua's Lua 5.4).

Run in the browser (WebAssembly)

A hosted demo is deployed automatically on every push to main, live at doublegate.github.io/RustySNES, alongside a PWA/offline-capable service worker and a <5 MiB gzip size budget enforced in CI. To build it yourself you need trunk (cargo install trunk):

cd crates/rustysnes-frontend/web
trunk serve            # dev server
trunk build --release  # the full winit + wgpu + egui build in ./dist
# Or a lightweight canvas-2D embed:
trunk build --release --no-default-features --features wasm-canvas

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Desktop UX

The desktop frontend frames the SNES image with an always-on menu bar (top) and status bar (bottom); the egui debugger is a separate overlay (behind the debug-hooks feature). Everything is reachable from the menu bar, and also from global keyboard hotkeys (v1.0.1): Escape=Quit, F1=Save State, F2=Reset, F3=Power Cycle, F4=Load State, F5=Rewind, F9=Save States… window, F11=Fullscreen, F12=Open ROM, Space=Pause/Resume, `=Toggle Debugger overlay (feature-gated: debug-hooks) — see rustysnes help hotkeys.

• Menu bar — File (Open ROM, Close ROM, Settings, Quit), Emulation (Pause/Resume, Reset, Power Cycle, Save/Load State (quick slot), Rewind, Save States… (10-slot thumbnail manager), Region, Speed 25%–300% presets, Window Size 1x–4x presets), Tools (Cheats / Netplay / RetroAchievements windows, each feature-gated), View (Integer scale, Post-filter (CRT / HQx), Performance panel, Fullscreen), Debug (the 7-panel debugger overlay, feature-gated).
• Settings window — a tabbed Video / Audio / Input / System dialog: present-mode radio, volume slider, 8 per-voice mute checkboxes (v1.0.1, a frontend/debug convenience — real S-DSP hardware has no per-voice mute register), a per-button key-rebind grid (click "Rebind", press the new key — Esc cancels), controller port 2 peripheral selection, region, HD texture pack selector, and light/dark/system theme.
• Performance panel — FPS, current speed, frame time, audio-ring health, and a rolling ~2-second frame-time sparkline — pure diagnostics, no controls.
• First-run welcome modal — a brief orientation shown once, the very first launch.

Default Controls

Every P1 binding is rebindable in Settings → Input (persisted to config.toml). USB gamepads auto-bind to P1 (Xbox-style: South = B, East = A, West = Y, North = X — the SNES diamond is rotated relative to Xbox's).

Action	Key
D-pad	Arrow keys
A / B	X / Z
X / Y	S / A
L / R	Q / W
Select / Start	Right Shift / Enter

Run rustysnes help controls / help gamepad for the full reference.

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Compatibility and Accuracy

RustySNES doesn't have one monolithic all-in-one oracle ROM (the way RustyNES's AccuracyCoin does for the NES) — no publicly available SNES ROM plays that role. Instead, accuracy is a composed multi-layer battery across independently-sourced suites (docs/testing-strategy.md); each layer's own status is tracked here, always current, reaffirmed every release:

Layer	Result
CPU (65C816) per-opcode oracle	0-diff — 5,119,999 / 5,120,000 (the one residual is a documented inter-reference divergence, not a bug — docs/adr/0002)
SPC700 per-opcode oracle	0-diff, 100.00% — 256,000 / 256,000
On-cart CPU (gilyon cputest-basic)	green — 1107 / 1107 "Success"
PPU/DMA/HDMA golden framebuffer (undisbeliever)	green, deterministic — 29 / 29 ROMs bit-identical
Audio boot+run (blargg spc_*)	literal PASS, all 4 — spc_smp, spc_timer, spc_mem_access_times, spc_dsp6
Core/Curated coprocessors (oracle-gated)	3 / 3, honesty gate green — DSP-1, Super FX/GSU, SA-1
BestEffort coprocessors, real-title validated	6 / 9 — DSP-2, DSP-4, ST010, S-DD1, CX4, OBC1
BestEffort coprocessors, unit-test only	3 / 9 — SPC7110 (ROM-sourcing gap, not a bug), ST018, S-RTC
Determinism contract	proven — bit-identical framebuffer/audio across runs; save-state round-trip proven across all three board tiers

Named residuals, tracked not hidden: the 65816 e1.e inter-reference divergence; DSP-3 and ST011 have no board wired yet; SPC7110's one locally available dump turned out to be a fan-translation ROM hack, not an original cartridge (a correctly-sourced dump is the actual remaining gap); PAL and ExLoROM both lack golden-ROM-boot proof (no ROM in the local corpus for either); hi-res (Modes 5/6) output is implemented and unit-verified but has no real-title validation yet. The full per-suite breakdown and the coprocessor coverage matrix live in docs/STATUS.md; the disposition of every one of these residuals (Remediated / No-stricter-oracle-available / Deferred / Out-of-scope) is tracked in docs/accuracy-ledger.md.

Everything shipped is additive and off-by-default — every optional feature (debug-hooks, scripting, cheats, netplay, retroachievements, hd-pack, emu-thread) is a frontend tap or opt-in flag, so the default/native/no_std/wasm builds stay byte-identical when off.

A note on test counts: RustySNES is validated by closed-form oracle ROMs (SingleStepTests, gilyon, undisbeliever, blargg) and per-coprocessor commercial-ROM suites, not by a headline unit test number alone (unit/integration tests run in cargo test --workspace, separate from the oracle suites above, which need --features test-roms). When a doc and a passing test ROM disagree, the ROM wins — that is this project's definition of "cycle-accurate."

_{An illustrative capability comparison against established SNES emulators — authoritative, always-current pass counts live in docs/STATUS.md, not this diagram.}

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Performance

The headless core is comfortably real-time. Against the 16.64 ms NTSC frame deadline:

Workload	Frame time	Headroom
headless_frame_steady_state (no-coprocessor ROM)	3.27 ms	~5.1× realtime

A CI frame-time regression gate (.github/workflows/ci.yml's bench job, scripts/bench_regression_check.sh) runs this benchmark on every release-tag push and fails on a gross (~3×) regression against a 10 ms absolute ceiling — a deliberately non-flaky gate, not a tight percentage check (shared CI runners are too noisy for that). The reproducible record (methodology, all benches, and save-state cost) is in docs/benchmarks.md.

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Platform Support

Platform	Status
Windows x64	Primary (release binary)
Linux x64	Primary (release binary)
macOS ARM64	Primary (release binary; Apple silicon)
WebAssembly	Primary (hosted demo + PWA/offline, deployed on every push to main)
Libretro Core	Supported (RetroArch via rustysnes-libretro)

System requirements

• Rust 1.96 stable (pinned via rust-toolchain.toml; auto-installed by rustup).
• A GPU with a wgpu-supported backend (Vulkan / Metal / DX12, or WebGL2 in the browser).
• The optional retroachievements / scripting features need a C compiler for their vendored C sources; the default build does not.

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Documentation

Document	Description
Project status matrix	Per-suite pass count, coprocessor coverage, feature flags, version policy — the single source of truth
Accuracy ledger	Every known approximation/divergence mapped to an explicit disposition
Architecture	System design and the load-bearing decisions
Frontend	The desktop/wasm shell, save states, pacing, the debugger overlay, scripting, netplay, RetroAchievements
Libretro core	rustysnes-libretro, a RetroArch-loadable core — build steps, manual verification, known scope cuts
CHANGELOG.md	Version history and release notes
Documentation handbook	The Material-for-MkDocs site rendering the subsystem specs (also on GitHub Pages)
Roadmap	The forward roadmap — the phase spine
Version plan	The named, versioned release ladder to v1.0.0 and beyond
Lockstep checklist	The process for tracking RustyNES's own continuing development before scoping each release

Hardware and subsystem specs

Component	Location
CPU (65C816)	docs/cpu.md
PPU (5C77/5C78)	docs/ppu.md
APU (SPC700/S-DSP)	docs/apu.md
Cartridges / coprocessors	docs/cart.md
Testing strategy	docs/testing-strategy.md

Architecture Decision Records live in docs/adr/. Deep hardware reference research lives in ref-docs/ (immutable). The full documentation map is docs/DOCUMENTATION_INDEX.md.

The hosted GitHub Pages deployment serves three sections from one artifact: the playable WebAssembly demo at doublegate.github.io/RustySNES, the workspace API docs (rustdoc) at doublegate.github.io/RustySNES/api/, and the Material-for-MkDocs documentation handbook at doublegate.github.io/RustySNES/docs/.

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Current Release

RustySNES's current release is v1.8.0 "Tracepoint". See docs/STATUS.md and CHANGELOG.md for the full release history (v0.1.0 through v1.8.0) and per-release detail.

• Download: the GitHub Releases page — desktop binaries for Linux, macOS (aarch64), and Windows.
• Full per-version history: CHANGELOG.md.
• Authoritative current state: docs/STATUS.md.

Roadmap

v1.0.0 — the production cut — shipped 2026-07-10, followed by v1.0.1 (per-voice audio mutes, global keyboard hotkeys), v1.1.0 (a research + accuracy pass), v1.2.0 (the Libretro core + CRT/HQx post-filters), v1.3.0 (HD texture packs), and v1.4.0 "Convergence" (the emu-thread-parity + accuracy-bugfix release that closed the post-v1.3.0 patch cluster).

Starting at v1.5.0, RustySNES entered the RustyNES-parity ladder: a multi-release plan to close the gap between this project's own feature/UX/accuracy maturity and its sibling NES emulator, tracked in lockstep rather than a frozen snapshot (to-dos/LOCKSTEP-CHECKLIST.md):

• v1.5.0 "Bedrock" — the CI safety net: cargo test --workspace now runs on every PR, not just tagged releases, behind a single required ci-success check.
• v1.6.0 "Lighthouse" — a Material-for-MkDocs documentation handbook, PWA/offline support for the wasm demo, and docs/accuracy-ledger.md.
• v1.7.0 "Telemetry" — the debugger overlay extracted into a dedicated debugger/ module, plus a live hex Memory panel.
• v1.7.1 — a patch release fixing two user-reported production bugs: the GitHub Pages Help menu under-reporting the running version (a Cargo.toml version-bump ceremony gap since v1.5.0), and the wasm demo's canvas rendering at a fixed, undersized 2x scale instead of the native 3x default.
• v1.8.0 "Tracepoint" — debugger depth II: a Memory Compare panel and an in-app Docs/glossary panel.

The full roadmap lives in to-dos/ROADMAP.md (the phase spine) and to-dos/VERSION-PLAN.md (the named release ladder, including the in-progress and planned rungs through the parity target).

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Contributing

Contributions of all kinds are welcome — code, testing, documentation, and design. Please read CONTRIBUTING.md for the quality-gate contract, the conventional-commit format, and the chip-behavior-change rule (a chip change touches both the code and its docs/<subsystem>.md in the same PR).

Quick contribution workflow

# 1. Fork and clone, then create a feature branch
git checkout -b feat/my-feature

# 2. Make changes and run the quality gates
cargo test --workspace
cargo clippy --workspace --all-targets -- -D warnings
cargo fmt --all --check

# 3. Commit using conventional commits, then push and open a PR
git commit -m "feat(cart): implement <thing>"
git push origin feat/my-feature

The quality gates (fmt, clippy, doc, and the test suite) run in CI on every PR that touches code (v1.5.0's CI safety net) and must be green; a pure-docs change skips them by design — see docs/adr/0011.

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License

RustySNES is dual-licensed under your choice of:

• MIT License — permissive, allows commercial use.
• Apache License 2.0 — permissive with a patent grant.

Unless you state otherwise, any contribution you submit is dual-licensed as above.

Test ROMs under tests/roms/ are individually CC0, MIT, or Zlib licensed. No commercial Nintendo ROMs are included, and they will never be bundled — dumps used for coprocessor validation are the user's responsibility and must come from cartridges they legally own (docs/adr/0003).

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Acknowledgments

RustySNES stands on the shoulders of giants:

• The SNESdev wiki and Nesdev wiki communities for decades of hardware documentation and forum research.
• Mesen2, higan, and ares as the accuracy reference bar and trace oracles.
• RustyNES, this project's own predecessor, for the Bus-owns-everything architecture, the frontend shell, the cargo full-build/CLI conventions, and the CI/docs-site infrastructure pattern ported here.
• SingleStepTests for the closed-form 65C816/SPC700 per-opcode oracle.
• undisbeliever and gilyon for the PPU/DMA/HDMA and on-cart CPU test-ROM suites.
• RetroAchievements and the rcheevos library that powers the achievement integration.

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Citation

If you use RustySNES in academic research, please cite:

@software{rustysnes2026,
  author  = {RustySNES Contributors},
  title   = {RustySNES: A Cycle-Accurate SNES Emulator in Rust},
  year    = {2026},
  version = {1.8.0},
  url     = {https://github.com/doublegate/RustySNES},
  note    = {Cycle-accurate SNES/Super Famicom emulator on a master-clock-precise scheduler;
             65C816 and SPC700 both 0-diff against SingleStepTests; 11 cartridge coprocessors
             (DSP-1, Super FX/GSU, SA-1, DSP-2/4, ST010, S-DD1, CX4, OBC1, SPC7110, ST018,
             S-RTC), save states with rewind/run-ahead, Lua 5.4 scripting with a deterministic
             TAS format, GGPO-style rollback netplay, RetroAchievements, and a multi-panel
             debugger; pure-Rust winit/wgpu/cpal/egui frontend with a WebAssembly build}
}

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