An NES emulator written in C++.
A to-do list, (roughly) in order of priority.
- All 6502 CPU opcodes implemented and working
- PPU implementation
- iNES memory mapper 0 [NROM]
- SDL gui
- PPU scrolling
- APU support
- memory mappers 1, 2
- save support
The code's pretty messy, since I've been prioritizing quantity of quality (at the moment). Here are a few things that I think can make it better.
- enums for addressing modes - especially since they're formulaic
- wrapper functions for things like EOR, AND, ORA, etc. since the only difference is addressing modes
- object organization -> master class for NES object
- consider passing object / struct as a parameter? instead of function signature changes
- refactor the opcode switch completely [low priority]
- have a instance variable for "extra cycle" flag
- use a function for detecting upper byte overflow?
- move enums and initializer lists to separate file
Smaller things to work on incrementally - more for me to not forget what I'm working on
- STA always increments cycle in favor of page turn - how to force this?
- unofficial opcodes, starting at LAX
- keep in mind that mapper 0 is hardcoded into current logic (but that's still 250 games)
- benchmark case-switch and check why it's so fast
- only update framebuffer for changed tiles in nametable
case-switch for all opcodes: ~6 microseconds (fa08c0d)
prebuilt opcode table: ~200 microseconds (8edcb51)
[checked with g++ nes.cpp -std=c++11 -O3 -g -fno-omit-frame-pointer and std::chrono]
- use latch in memory.cpp to take advantage of quickness of pure case switch and still do memory-mapped i/o (ppu, dma, etc) [maybe]
