nes-emu

A Nintendo Entertainment System (NES) emulator written in C++

As this is just a pet project, don't expect a full-featured emulator. There is no GUI, many typical features are missing, and only a few mappers have been implemented. However, the code is pretty clean and straightforward, and I think can be useful to learn from. Of course, if someone wanted to fork this code to write a full-featured emulator, that would be cool as well :)

Features

• Mappers 0,1,2,3,4,7 (~90% of games)
• Accurate audio emulation (no DMC)
• Automatic saving of SRAM
• Save state support
• Rewind any time up to 1 minute at normal speed
• Single and multi frame stepping when paused

Controls

Input	Keyboard Key(s)
D-Pad	arrows
A	A
B	S
Select	Tab
Start	Enter

                  |

Open Rom | Ctrl + O Reset | Ctrl + R Quit | Alt + F4 | Rewind | Backspace Pause | P Step frame | [ Step many frames | ] | Toggle audio channels | F1-F4

Challenge

As with most pet projects, the purpose of writing this emulator was mainly to learn. My background is not in hardware, but I have always had a keen interest in computer architecture, so part of my goals was to learn more about how a console works at the hardware level. The NES is simple enough in that respect, although it has enough quirks to make it interesting to emulate.

To further my learning, I challenged myself to write this emulator without looking at any other emulator code. So the implementation is completely my own, and I suspect parts of my code may seem strange or inefficient as compared to other implementations.

Building

• Install CMake

• Download 32-bit SDL2 Development Libraries from https://www.libsdl.org/download-2.0.php

  • On Windows, set an environment variable named "SDL2" to the path of the extracted archive (e.g. set SDL2=C:\code\SDL2-2.0.4)
  • On Debian Linux, install SDL2: sudo apt-get install libsdl2-dev

• Run CMake and build. For example, on Windows:

cd nes-emu
md build
cd build
set SDL2=C:\code\SDL2-2.0.4
cmake ..

Thanks

Although I did not look at other emulator source code, I did get a lot of information and help from other sources:

• The awesome people on the #nesdev IRC channel (huge thanks!)
• Excellent documentation on the nesdev wiki
• Other excellent emulators I used to compare output, trace, and debug:
  • fceux
  • Nintendulator
  • NO$NES