N64 Emulator Development Status

Last Updated: January 6, 2026
Status: Basic implementation with functional RDP graphics processor
ROM Tested: Test ROMs (WORKING - rectangles, triangles), Commercial ROMs (NOT PLAYABLE - require RSP)

Overview

For detailed implementation information, see:

Current Implementation Status

✅ Working Components

Core System:

  • ✅ MIPS R4300i CPU - Complete instruction set implementation from emu_core::cpu_mips_r4300i
  • ✅ Memory Bus - 4MB RDRAM, PIF boot, SP memory, cartridge ROM
  • ✅ Cartridge Loading - Z64/N64/V64 formats with byte-order conversion
  • ✅ Save States - Full system state serialization

Graphics (RDP):

  • ✅ OpenGL Hardware Renderer - GPU-accelerated rendering (REQUIRED)
  • ✅ 3D Triangle Rendering - Flat shading, Gouraud shading, Z-buffer depth testing
  • ✅ Display List Processing - RDP command execution
  • ✅ Basic RDP Commands - Fill, scissor, sync operations
  • ✅ Test ROM Rendering - Colored rectangles and simple 3D scenes work correctly

⏳ Partially Working / In Development

RSP (Reality Signal Processor):

  • ⏳ Basic Infrastructure - Stub implementation in place
  • ❌ Microcode Execution - Not implemented (required for commercial games)
  • ❌ Geometry Processing - Not implemented

Graphics:

  • ⏳ Texture Mapping - TMEM structure in place, sampling not fully implemented
  • ⏳ Advanced RDP Commands - Many commands stubbed or missing

❌ Not Implemented

  • ❌ Audio - Audio interface not implemented
  • ❌ Controller Input - Input system not implemented
  • ❌ Memory Management - No TLB, cache, or accurate timing
  • ❌ Commercial Game Support - RSP microcode execution required

Renderer Architecture

The N64 RDP now uses OpenGL 3.3+ hardware-accelerated rendering exclusively. Software renderer has been removed to simplify the codebase and ensure consistent GPU performance.

OpenGL Renderer (Required)

  • ✅ GPU-accelerated rendering using OpenGL 3.3 Core Profile
  • ✅ Hardware depth testing - Leverages GPU Z-buffer
  • ✅ Full triangle rendering - Flat shading, Gouraud shading, textured triangles
  • ✅ Feature parity - All RDP rendering capabilities
  • ✅ Default feature - OpenGL is now part of default features (always enabled)
  • Requirements: OpenGL 3.3+ compatible graphics hardware

Architecture Changes (January 2026)

  • ❌ Software renderer removed - Deleted ~850 lines of CPU-based rasterization code
  • ✅ Simplified initialization - RDP created directly with OpenGL renderer
  • ✅ Mandatory GL context - N64System::new() requires glow::Context parameter
  • ✅ No renderer switching - Renderer is fixed at system creation time

Testing

Test ROMs

The test_roms/n64/ directory contains basic test ROMs that verify:

  • RDP fill command rendering
  • Display list processing
  • Triangle rasterization
  • Z-buffer depth testing

Build test ROMs with:

cd test_roms/n64
./build.sh

Running Tests

Note: N64 tests require an actual OpenGL context and are marked as #[ignore] for CI.

# Run all N64 tests (non-GL tests only)
cargo test --package emu_n64

# Run all tests including GL-dependent tests (requires OpenGL 3.3+)
cargo test --package emu_n64 -- --ignored

Known Limitations

See MANUAL.md for complete user-facing limitations.

Critical blockers for commercial games:

  1. No RSP microcode execution - Cannot process geometry from games
  2. No texture mapping - Only flat/shaded triangles (TMEM structure exists but sampling incomplete)
  3. No audio - Audio interface not implemented
  4. No controller input - Input system not implemented
  5. Frame-based timing - Not cycle-accurate

System Requirements:

  • OpenGL 3.3+ required - No software fallback available
  • Compatible graphics hardware with OpenGL 3.3+ support

Development Priorities

For detailed development roadmap, see the N64 README.

Short Term

  1. Complete texture sampling implementation
  2. Expand RDP command coverage
  3. Improve VI integration

Medium Term

  1. RSP microcode execution (essential for commercial games)
  2. Audio interface implementation
  3. Controller input support

Long Term

  1. Cycle-accurate timing
  2. TLB and cache emulation
  3. Commercial game compatibility

Building and Debugging

Build Commands

# Default (OpenGL renderer - always enabled)
cargo build --package emu_n64 --profile release-quick

# Frontend with N64 support
cargo build --profile release-quick

Debug Logging

# CPU execution trace
cargo run --profile release-quick -- rom.z64 --log-cpu trace

# Interrupt debugging
cargo run --profile release-quick -- rom.z64 --log-interrupts info

# PPU/graphics debugging
cargo run --profile release-quick -- rom.z64 --log-ppu info

References

Documentation

Hardware Reference

Change History

This document tracks high-level status. For detailed change history:

  • See git commit log for implementation changes
  • See N64 README for architecture and component details
  • Historical detailed session logs have been archived

Major Milestones:

  • January 2026: OpenGL renderer made mandatory, software renderer removed (~850 lines)
  • January 2026: Basic RDP rendering, test ROMs working
  • December 2025: Initial MIPS R4300i CPU implementation
  • November 2025: Project structure and core components

Document Status: This is a high-level status overview. For implementation details, always refer to the N64 System README.