Super Castlevania IV Recomp

Super Castlevania IV Recomp

A native recompilation of Super Castlevania IV (USA), built on snesrecomp.

Super Castlevania IV is a 1991 platform game developed and published by Konami for the Super Nintendo Entertainment System. It has been re-released multiple times, including for the Super NES Classic Edition.

Description from Wikipedia, CC BY-SA 4.0.

You must legally own a copy of the game. No ROM data is distributed with this project, in the repository or in any release. The recompiled C is generated locally from your own copy and is never committed.

☕ Keep the ports coming

This project is free and always will be. Every port in this series, Super Castlevania IV included, is built with many hours of AI-assisted reverse engineering, and that AI time is paid. If you enjoy playing it, a coffee at buymeacoffee.com/mpolizel keeps the AI running so more SNES games can be ported to native Recomp. Any amount helps, and thank you!

Download (ready-to-run Windows build)

Get the latest supercastlevania4-<version>-windows-x64.zip from the Releases page.

The zip is a setup pack: it contains the launcher, the recompiler and this source tree (with the framework patches already applied), but no game data. On first run:

1. Unzip anywhere and start SuperCastlevaniaIvSNESRecomp.exe.
2. Let it download the portable build tools (one time per machine), or point it at a cmake-clang-v1 zip you already have.
3. Pick your own Super Castlevania IV (USA).sfc (CRC32 b64ffb12).
4. Press Generate & rebuild. The playable game is built into build/ and started; run it from there afterwards.

In the launcher, Settings → Shader lists the scanline, CRT and upscaler presets; choosing one switches the renderer to OpenGL automatically. A fresh install starts with no shader (the plain picture), the lightest option for any graphics card; pick a CRT or upscaler preset there if yours has room. Your choice is saved in config.ini and kept. The upscalers include ScaleFX and the neural NNEDI3 presets.

During play, Ctrl+L (or Select+L3 on a controller) reopens the launcher: shader, window scale, volume and controls apply when you press Resume, without restarting the game. I cycles the audio interpolation between Gaussian (the console's own, the default), Cubic (crisper highs) and Sinc; it only changes what you hear, never the game, and the choice is saved in audio_interpolation.txt.

On laptops with two graphics cards (NVIDIA Optimus, AMD switchable graphics) the game asks the driver for the dedicated one. If it still runs slowly, set the game's executable to High performance in Windows Settings → System → Display → Graphics.

Updates

With Check for updates on start ticked (the default; on the launcher's main screen, next to Skip launcher on boot), the game asks GitHub for the latest release when it starts and offers to install a newer one. Accepting closes the game, downloads the new setup pack, copies it over the install folder and reopens the setup window: press Generate & rebuild. Nothing is deleted; build\ (the rebuilt game, save states, config.ini, keybinds.ini) and rom.cfg are kept. Untick the box to turn the check off (saved in update.ini).

The game has no battery save: progress is kept by its passwords.

Your saves are never lost or broken by an update. Save states made by any earlier release keep working in every later one. Before installing, the updater copies build\saves\ to save-backups\<date>_before_<version>\ and never deletes those copies; save files are left out of the copy, and if they changed anyway the backup is put back. Every release is checked against the one before it with tools/check_update_compat.ps1, which builds the previous release, makes a save state with it, installs the new pack with the previous release's own updater and rebuilds; it fails unless every save file is byte-identical and the new build continues the old save state.

See CHANGELOG.md for what changed in each release.

Status

Boots through the Konami logo, the intro and the title screen into name entry, the opening cutscene and the first stage (Block 1-1), which plays: walking, whipping, pickups, death and restart. Most code still runs through the snesrecomp interpreter; later stages are not yet verified. See Porting from here.

Framework patches

patches/ holds changes to the snesrecomp and recomp-ui submodules. Reapply them after updating the submodules:

git -C snesrecomp apply ../patches/snesrecomp-audio-interpolation.patch
git -C snesrecomp apply ../patches/snesrecomp-glsl-passprev-and-vao.patch
git -C snesrecomp apply ../patches/snesrecomp-nmi-idle-loop-wai.patch
git -C snesrecomp apply ../patches/snesrecomp-nmi-nested-wait.patch
git -C snesrecomp apply ../patches/snesrecomp-raster-oam-and-hdma.patch
git -C snesrecomp apply ../patches/snesrecomp-shader-forces-opengl.patch
git -C recomp-ui apply ../patches/recomp-ui-host-toggle.patch

snesrecomp-nmi-nested-wait.patch is required for this game (it applies on top of snesrecomp-nmi-idle-loop-wai.patch). Super Castlevania IV runs its game logic inside the NMI handler and waits there for the next NMI: $00:854B writes $80 to $3C and spins until the next NMI writes 1. On hardware that NMI interrupts the waiting handler. The interpreter ran the handler to its step cap instead, so the wait never ended and the game ran off the rails on its first frame (an IRQ/BRK storm). With the patch a host-invoked handler still running at the end of the field is parked like the main thread, the next field delivers its NMI on top of it, and the handler's own RTI later returns to the interrupted main program.

snesrecomp-raster-oam-and-hdma.patch is the renderer fix shared with the other ports: per-line sprite tables, HDMA set up in vblank, and vblank writes kept in their own field. It also counts HDMA's first transfer, made in V=0's H-blank, as a table line, as the hardware does. Every HDMA split landed one line late without it (on Donkey Kong Country 2's island map the late layer split drew a bright line across the screen).

snesrecomp-audio-interpolation.patch adds the Cubic and Sinc audio interpolation (I key). They resample the dry output only; the echo buffer, OUTX, pitch modulation and save states stay those of the console's Gaussian filter, so the game runs identically in every mode.

snesrecomp-glsl-passprev-and-vao.patch fixes two shader bugs: a pass that reads PassPrev<n> back to the game frame got nothing (ScaleFX drew black), and switching to no shader mid-game drew a black screen because the shader path left the plain path's vertex attributes disabled.

recomp-ui-host-toggle.patch lets a title add one checkbox of its own beside "Skip launcher on boot"; this project uses it for the update check.

ROM identity

File	Super Castlevania IV (USA).sfc
Publisher	Konami
Developer	Konami
Year	1991
Mapping	lorom
Region	USA (North America)
Coprocessor	none
CRC32	b64ffb12
SHA-256	0ef6f4cce5a2273fa49fe1ce724e0048a8e39c91da6b00dbb693fe1ba909177d

tools/regen.sh refuses to run against anything else, so a mismatched revision fails immediately instead of producing subtly wrong output.

Build

git submodule update --init --recursive
bash tools/regen.sh --rom "/path/to/Super Castlevania IV (USA).sfc"
cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j

The ROM does not have to live in the repository — keeping it on your own drive is the better habit, and SNESRECOMP_ROM sets the path once for a shell. Without either, tools/regen.sh finds the ROM at the repo root, then the path the setup wizard recorded in rom.cfg; .gitignore blocks both from ever being committed.

tools/regen.sh verifies the ROM, generates src/gen/*.c, and re-syncs recomp/funcs.h. Re-run it whenever you change anything under recomp/.

The Windows build is a window app: diagnostics go to SuperCastlevaniaIvSNESRecomp.log beside the executable. -DSCIV_CONSOLE=ON brings the console back for debugging.

Run

./build/SuperCastlevaniaIvSNESRecomp                    # launcher picks the ROM
./build/SuperCastlevaniaIvSNESRecomp "/path/to/Super Castlevania IV (USA).sfc"

With no ROM on the command line the build opens the recomp-ui launcher: a ROM picker with a verification badge, plus display / audio / input settings. Your choice is cached in rom.cfg beside the executable, so the next launch opens on it and "Skip launcher on boot" makes it immediate.

Either way the ROM is checked against the digests above before anything boots — a dump that could not have produced this build is refused at the door rather than mis-executing ten frames in.

Layout

Path	What lives there
recomp/	Analysis input: bank*.cfg, symbols.toml, generated funcs.h
rom_identity.txt	ROM digests — read by the build, tools/regen.sh and CI
src/	Host code you own: main.c, game_rtl.c, sciv_update.c
src/gen/	Generated C. Never committed — regenerate locally
assets/shaders/	Scanline, CRT and upscaler presets for the launcher
patches/	Changes to the framework submodules (see above)
snesrecomp/	Framework submodule (owns lib/recomp-net, lib/retcomm-rbengine)
tools/	regen.sh — the ROM → C pipeline; import_libretro_shaders.py
scripts/	package_release.sh — player-facing zip
framework_pins.txt	Exact framework commits this project was scaffolded against

Porting from here

The scaffold stops where the game-specific work starts. In rough order:

1. Make it boot. src/game_rtl.c holds the frame driver. It starts on the framework's beam-aligned driver (snesrecomp/runner/src/beam_frame_driver.h): one frame per PPU field, interrupts taken where the beam latches them, the field rasterized from the raster journal.
2. Name things. Add entries to recomp/symbols.toml as you identify routines, then re-run tools/regen.sh. Set emit = true to promote one into ahead-of-time analysis; leave it false to keep it interpreted. See recomp/README.md.
3. Resolve dispatch misses. After every run, deal with unresolved indirect targets before anything else — they are the reason a port diverges, and they are cheap to fix early.
4. Never synthesise a result to get past uncovered code, and never edit src/gen/ by hand. Fix the config or the framework and regenerate.

Players

One player.

License

This project's own source is under the MIT license in LICENSE. The framework carries its own terms (PolyForm Noncommercial 1.0.0) — see snesrecomp/LICENSE and snesrecomp/THIRD_PARTY_ATTRIBUTION.md; the changes in patches/ apply to that framework and fall under its terms. The shaders under assets/shaders/_libretro/ come from libretro/glsl-shaders and keep each author's license in their file headers. None of these cover the game data, which is not distributed here.

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