Bisqwit demonstrates how to build an accurate NES emulator in C++ using compile-time template metaprogramming for instruction decoding.
In this tool-assisted education video I create a NES emulator with C++0x. ENABLE CAPTIONS!
The emulator is very accurate, and sort-of portable; it compiles on any architecture that support libSDL, but it outputs audio through an external program and reads joypad input from a file.
This video is part 1/2.
-- Part 1 (
youtu.be/y71lli8MS8s ): Creating the emulator.
-- Part 2 (
youtu.be/XZWw745wPXY ): Compiling and running.
Twitter:
twitter.com/RealBisqwit
Patreon:
patreon.com/Bisqwit (alternatives at
iki.fi/bisqwit/donate.html)
Twitch:
twitch.tv/RealBisqwit
Homepage:
iki.fi/bisqwit/
The source code is about 940 lines in total.
Download & FAQ & resources:
bisqwit.iki.fi/jutut/kuvat/programming_examples/nesemu1/
Approximate count of lines of code per topic, in the source code:
- 20 lines, CPU: Declarations (registers, flags and internal memory)
- 100 lines, CPU: Interpreting and executing CPU opcodes & signals
- 100 lines, CPU&GamePak: Memory mapping (iNES mappers 0,1,2,3,7 are supported)
- 40 lines, PPU: Declarations (registers and emulator-specific status variables)
- 50 lines, PPU: Memory mapping and I/O
- 180 lines, PPU: Rendering and timing control
- 30 lines, PPU & IO: Joypad updating (PPU provides the timing for input-file access)
- 40 lines, PPU & IO: Color NTSC emulation (converting NES colors into RGB through NTSC modem)
- 15 lines, IO: libSDL initialization and rendering
- 35 lines, main&IO: ROM loading from file, initialization and emulation loop
- 200 lines, APU: Sound emulation (of which 40 lines are because of DMC/DPCM support)
- 130 lines, (other, such as comments, and inaccuracies in the above numbers)
Check out MaiZure’s excellent walkthrough of the source code of the emulator from this video!
maizure.org/projects/decoded-bisqwit-nes-emulator/
Background music: Jinguuji detective series. It was difficult to choose. I wanted good NES music, but I did not want it to too recognizable. I intended to convert something, but I had already spent months on this video... It was getting late.
Because of the 15 minute limit that YouTube was imposing on my account when I made this video, I had to develop many techniques to shorten the code dramatically. I also had to type it very quickly… And I had to split the actual demonstration into a second video.
I use C++11 exclusive techniques extensively in the code. I am particularly proud of the CPU emulator. It is cycle and memory access accurate, and feature-complete. It is not very slow, either. It is only 100 lines long, thanks to a number of clever ideas. I thank byuu for a particular idea that helped make it horizontally shorter. Each if() in ins() is completely parsed and evaluated at compile-time. Effectively the compiler synthesizes 259 distinct ins() functions, each performing only the particular opcode's worth of work.
I architected all the components in as close conformance as I could to whatever documentati
