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 The source-downloads there do not seem to be updated by the Github-action used to handle making releases, so are out of date.

Compiling

MacOS (plain executable)

This build depends on SDL2 being installed with homebrew.

MacOS (app-bundle)

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

Linux

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.

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.

ButtonKey
UpUp arrow
DownDown arrow
LeftLeft arrow
RightRight arrow
StartEnter
SelectRight shift
AX
BZ
XS
YA
LD
RC

Additionally, the following command are available:

KeyAction
RSoft reset
EHard reset
PPause
OFrame advance
TTurbo (hold)
LRun one CPU cycle
KRun one SPC cycle
JDumps some data
MMake save state
NLoad 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