go-nes is a focused, well-tested Go library that implements the core internals of an NES emulator. It intentionally excludes GUI and real hardware I/O (display/windowing, real controllers, audio output). The goal is to provide a clean, reusable emulator core you can embed into your own frontend, educational tooling, or testing harness.

• Accurate 6502 CPU emulation with support for all official/unofficial opcodes and addressing modes.
• Passed the NESTest CPU test ROM for accuracy verification of 6502 instructions and unofficial opcodes.
• Basic PPU implementation for rendering graphics (background and sprites).
• APU stubs for audio processing (full audio implementation is a work in progress).
• Memory mapping that supports various NES mappers (NROM, MMC1, etc.).

• nes: High-level NES struct that ties together CPU, PPU, APU, and memory.
• cpu: Implements the 6502 CPU with all instructions, addressing modes, and status flags.
• ppu: Handles the NES Picture Processing Unit (PPU) for graphics rendering.
• apu: Manages the NES Audio Processing Unit (APU) for sound generation.
• memory: Emulates the NES memory map, including RAM, ROM, and I/O registers.
• rom: Loads and parses NES ROM files in iNES format.
• rom/ines: Loads and parses iNES header.
• rom/mapper: Supports various NES cartridge mappers for memory banking.
• controller: Emulates NES controller input handling.

• NROM (Mapper 0)

There are a minimal example of how to use the library to load a ROM and run the emulation loop:

// Import the library
import "github.com/ghosind/go-nes"

// Read a ROM file
romData, err := os.ReadFile("path/to/your/game.nes")

// Create a new NES instance
myNes, err := nes.New(romData)

// Run the emulation loop
for {
    myNes.Step() // Step the CPU, PPU, and APU
    // Handle input, rendering, etc.
}

The project includes extensive unit tests covering CPU instructions, memory mapping, and ROM loading. To run all tests, use:

go test ./...

To run tests for a specific package, e.g., CPU:

go test ./cpu -v

• 6502 CPU implementation with unofficial opcodes
• Complete NESTest compliance
• Memory mapping and RAM emulation
• iNES ROM loading and parsing
• IRQ and NMI handling
• Complete NROM mapper support (mapper 0)
• PPU implementation for full graphics rendering
• APU implementation for audio output
• Support for additional mappers (MMC1, MMC3, etc.)
• Controller input handling
• Debugging and logging utilities

• NES Documentation
• CPU Reference
• Obelisk 6502 Guide
• Unofficial 6502 Opcodes
• PPU Programmer Reference
• iNES File Format
• INES 1.0 Mapper Grid

This project is licensed under the MIT License - see the LICENSE file for details.