NES-Emulator

An incomplete NES emulator made using SDL2 and C++23.

Roadmap

• Basic source code layout
• ROM file input and processing
• Continuous integration / static analysis tool setup
• Official CPU opcode emulation
• Full unofficial CPU opcode emulation
• Finish nestest support
• Additional CPU tests
• PPU emulation
• Display support
• Mapper support
• Testing with game ROMs

Quick-Start Instructions

Prerequisites

• cmake
• gcc / MSVC (with C++23 standard)
• libsdl2-dev (if on Linux)

In order to build the project, run

cmake --preset=<target-preset> # See available presets with --list-presets
cmake --build build

This will create a build folder in the repository and build the project from the source.

Alternatively, building should be possible with the Ninja and Visual Studio 18 2026 generators, as well. Examples of these are shown in the GitHub Actions automated builds.

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References

• NES memory mapping: https://fceux.com/web/help/NESRAMMappingFindingValues.html
• NES emulator in JS: https://web.archive.org/web/20210624190954/http://blog.alexanderdickson.com/javascript-nes-emulator-part-1
• NES memory mapping: https://en.wikibooks.org/wiki/NES_Programming/Memory_Map
• 6502 instruction set: https://web.archive.org/web/20140619200254/http://www.obelisk.demon.co.uk/6502/reference.html (no longer active)
• 6502 addressing modes: https://web.archive.org/web/20150128022425/http://www.obelisk.demon.co.uk/6502/addressing.html (no longer active)
• iNES file format: https://www.nesdev.org/wiki/INES
• List of games by mapper: https://nesdir.github.io/mapper0.html
• NES addressing modes: https://www.nesdev.org/wiki/CPU_addressing_modes
• 6502 opcodes: http://www.6502.org/tutorials/6502opcodes.html
• More 6502 opcodes (with cycle counts): http://www.oxyron.de/html/opcodes02.html
• Status flags: https://www.nesdev.org/wiki/Status_flags
• Detailed opcode descriptions: http://www.romdetectives.com/Wiki/index.php?title=AND
• Reference implementation: https://github.com/fogleman/nes
• NES overflow flag: http://www.righto.com/2012/12/the-6502-overflow-flag-explained.html
• NES opcode timing: http://atarihq.com/danb/files/64doc.txt
• nestest CPU test: http://www.qmtpro.com/~nes/misc/nestest.txt
• Stack pointer and nestest: https://www.reddit.com/r/EmuDev/comments/g663hk/nestestlog_stack_pointer_starting_at_fd_and_sbc/
• BRK/IRQ/NMI/RESET and stack pointer behavior: https://www.pagetable.com/?p=410
• BRK command behavior: http://www.romdetectives.com/Wiki/index.php?title=BRK
• Detailed opcodes list: https://www.masswerk.at/6502/6502_instruction_set.html
• ADC and SBC commands: https://stackoverflow.com/questions/29193303/6502-emulation-proper-way-to-implement-adc-and-sbc
• NES PPU explanation: https://www.reddit.com/r/EmuDev/comments/evu3u2/what_does_the_nes_ppu_actually_do/
• PPU rendering guide: https://www.nesdev.org/wiki/PPU_rendering
• PPU frame timing: https://www.nesdev.org/wiki/PPU_frame_timing
• CPU power-up information: https://www.nesdev.org/wiki/CPU_power_up_state
• NES APU register guide: https://www.nesdev.org/wiki/APU_registers
• NES emulator guide for Rust: https://bugzmanov.github.io/nes_ebook/chapter_5_1.html
• NES mapper explanation: https://www.reddit.com/r/EmuDev/comments/cyrowl/mappers_and_nes/
• Interesting NES mapper exploration: https://somethingnerdy.com/unlocking-the-nes-for-former-dawn/
• Explanation of mappers and bank switching: https://somethingnerdy.com/mappers-matter/
• NES test ROM collection: https://github.com/christopherpow/nes-test-roms
• NES input data and registers: https://stackoverflow.com/questions/66406934/whats-an-elegant-way-to-read-controller-input-for-nes-6502-assembly-on-ca65
• PPU registers: https://www.nesdev.org/wiki/PPU_registers
• List of NES mappers: https://www.nesdev.org/wiki/Mapper
• NES emulator in Rust: https://bugzmanov.github.io/nes_ebook/chapter_1.html
• CPU / PPU synchronization discussion: https://www.reddit.com/r/EmuDev/comments/10m9had/cpu_ppu_timing_catch_up_method/