LakeSnes

A SNES emulator, in C

About

This is a SNES emulator, written in C, mostly as a followup on my earlier Javascript version. The main drive behind rewriting it in C was C's speed. The JS version could barely run at 20 FPS on my system, whereas this C version runs at full speed.

The intent is for the actual emulation itself to be split off into a library, which can then be used in other projects. (Maybe it could be compiled for the web with Emscripten as well, to replace the core from that JS emulator). This is not done yet, and as of now a full emulator with basic frontend (using SDL2) is build.

Performance, although much better than my JS version, is still quite bad though, especially when compared to emulators like BSNES or SNES9X (it used around 80% of one core whereas SNES9X only used around 15%, on my old hardware).

Nightly releases

Nightly builds can be downloaded from the releases here. The source-downloads there do not seem to be updated by the Github-action used to handle making releases, so are out of date.

• The macOS build is an app-bundle (includes SDL2) but not signed and notarized, and does not have proper version information. These are currently Intel-only, although manually compiling for/on Apple Silicon (arm64) works without issues. It might not run on older macOS versions.
• The Linux build depends on SDL2 being installed already and is an x86_64 (64-bit Intel) build.
• The Windows build includes SDL2.dll and is a 64-bit (Intel) build.

Compiling

MacOS (plain executable)

• Install homebrew (This also install the Xcode CLI-tools, providing clang and make)
• Install SDL2 with homebrew: brew install sdl2
• Run make

This build depends on SDL2 being installed with homebrew.

MacOS (app-bundle)

• Make sure clang and make are available (from the Xcode CLI-tools)
• Download the latest SDL2 build (the .dmg) from the SDL2 Releases
• Create a directory called sdl2 in this repo's directory and copy SDL2.framework from the dmg into it
• Run make LakeSnes.app

This is a stand-alone application (includes SDL2) and shows up in the 'open with' menu for smc, sfc and zip files.

Linux

• Make sure clang (or gcc) and make are available
• Get SDL2-dev via the package manager (Ubuntu/Debian: sudo apt install libsdl2-dev)
• Run make (or make CC=gcc to use gcc)

This build depends on SDL2 being installed.

Windows

NOTE: Only tested with Msys2 using clang for x86_64, but building for arm64 should work as well, and using gcc, other environments, other tools (Cygwin, Mingw, etc) or Visual Studio might also be possible. Some changes might be needed due to some of the includes and functions used.

• Install Msys2
• Open a clang64 environment (and run pacman -Suy)
• Install clang and make: pacman -S mingw-w64-clang-x86_64-clang mingw-w64-clang-x86_64-make
• Install SDL2: pacman -S mingw-w64-clang-x86_64-SDL2
• Navigate to this repo's directory (cd /c/Users/...)
• Run mingw32-make lakesnes.exe (or mingw32-make to build iconless exe)
• Run cp /clang64/bin/SDL2.dll . (to copy SDL2.dll)

This build depends on SDL2.dll being placed next to the executable.

Usage and controls

The emulator can be run by opening lakesnes directly or by running ./lakesnes, taking an optional path to a ROM-file to open. ROM-files can also be dragged on the emulator window to open them. ZIP-files also work, the first file within with a .smc or .sfc will be loaded (zip support uses this zip-library, which uses Miniz, both under the Unlicence).

Currently, only normal joypads are supported, and only controller 1 has controls set up.

Button	Key
Up	Up arrow
Down	Down arrow
Left	Left arrow
Right	Right arrow
Start	Enter
Select	Right shift
A	X
B	Z
X	S
Y	A
L	D
R	C

Additionally, the following command are available:

Key	Action
R	Soft reset
E	Hard reset
P	Pause
O	Frame advance
T	Turbo (hold)
L	Run one CPU cycle
K	Run one SPC cycle
J	Dumps some data
M	Make save state
N	Load save state

Alt+Enter can be used to toggle fullscreen mode.

L will run one CPU cycle, and then logs the CPU state (opcode, registers, flags). K does the same, but for the SPC instead (note that this acts as additional SPC cycles).

J currently dumps the 128K WRAM, 64K VRAM, 512B CGRAM, 544B OAM and 64K ARAM to a file called dump.bin.

Battery saves, save states and dump.bin are stored in the SDL-provided preference directory, this is usually in ~/Library/Application Support/LakeSnes on macOS, ~/.local/share/LakeSnes on Linux and %USERPROFILE%\AppData\Roaming\LakeSnes on Windows. Battery saves go in a subdirectory saves and save states in states. Battery saves and save states are currently named after the roms full name without extension, with .srm or .lss appended respectively.

Note that the save state format and exact naming and location for battery saves and save states is still being worked on and subject to change. Further updates will likely break compatibility with older save states and battery saves might need to be moved around and/or renamed.

Minimizing or hiding the window can cause high CPU usage as this can cause v-sync to stop working.

Compatibility

The emulator currently only supports regular LoROM, ExLoROM, HiROM and ExHiROM games. Capcom CX4 is the only co-processor emulated at this time. SPC files can not be loaded yet, but are planned.

This emulator is definitely not fully accurate. The PPU renders per scanline, so mid-scanline effects are not supported. The DSP executes on a per-sample basis. The SPC and CPU-side timing should be cycle-accurate now.

Quite a few TODO's are scattered throughout the code for things that are currently not quite fully emulated, mostly related to edge cases and some lesser-used PPU features.

Some things that are not emulated at all are full emulation-mode for the 65816, and the test-register ($f0) for the SPC.

Some games that I have tested seem to run without obvious issues, bugs.md contains a non-exhaustive list of games that have emulation-bugs.

License

This project is licensed under the MIT license, see 'LICENSE.txt' for details.

It uses 'kuba--/zip' which is under the Unlicense, and links against SDL2 which is under the zlib license.

Resources

• The WDC datasheet for the W65C816S cpu.
• The 65C816 opcodes tutorial from 6502.org.
• The 65816 opcode matrix from oxyron.de (the cycle timing and notes there aren't fully accurate, and the addressing modes IAL and IAX are swapped for JMP (opcodes $7C and $EC)).
• The SuperFamicon wiki.
• The SnesDev Wiki by Sour (seems to be abadoned).
• The SnesDev Wiki at NesDev.
• Some quick peeks at Sour's Mesen-S source, nuw superseeded by Mesen 2.
• Some quick peeks at Higan's source, Bsnes' source and Ares' source, all formely by Near.
• The nocach fullsnes document.
• Some posts and resources in the SnesDev section of the NesDev forums.
• The Super NES Programming pages in Wikibooks.
• Anomie's docs from Romhacking.net.
• Various roms (especially the CPU tests) by PeterLemon/krom found here.
• The 65816 tests by TomHarte found here.
• The SPC700 tests by raddad772 found here (part of JSmoo, a JS-based set of emulators; tests also included in TomHarte's repo).
• Various SPC and DSP test by Blargg (from here and here).
• The source for the BRR-tools from SMW central, found here.
• SDL2 is used for the frontend window/rendering/audio/input handling.
• This zip-library is used for zipped rom loading support.