strugglemeat/lakesnes

A SNES emulator, in C

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 it to be formed as a library, which could 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).

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).

Compiling

Linux

• Make sure gcc and make are available (sudo apt install build-essential)
• Get SDL2-dev via the package manager (sudo apt install libsdl2-dev)
• Run make

Note that these build are dependend on SDL2 being installed / found in ./sdl2.

Usage and controls

The emulator can be run with ./lakesnes and takes 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
T	Turbo

Alt+Enter can be used to toggle fullscreen mode.

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 and HiROM games (no co-processors and such). Battery saves are not retained yet. SPC files can also not be loaded yet.

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 is currently still opcode-based (although the SPC core itself is cycle-accurate). The CPU-side timing should be cycle-accurate now, but the exact timing of certain event is still somewhat off. Communication between the CPU and SPC is also not cycle-accurate.

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, although some games do seem to glitch somewhat or freeze. 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.

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.
• Some quick peeks at Byuu's Higan source.
• The nocach fullsnes document.
• Some posts and resources in the SnesDev section of the NesDev forums.
• The Super NES Programming pages in Wikibooks.
• 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.
• This zip-library is used for zipped rom loading support.