Running .NET on the NES - Jonathan Peppers - NDC Oslo 2024

Project demonstrates running C# code on the Nintendo Entertainment System (NES) through a custom build process that converts .NET IL to 6502 assembly

NES technical constraints include:

• Less than 2MHz processor
• 52 available colors (25 simultaneously)
• Maximum cartridge size ~512KB
• No garbage collection
• Big endian architecture

Implementation approach:

• Created reference assembly with 44 core methods to match NES-lib C library
• Uses MSBuild tasks to convert IL to 6502 assembly during build
• Hooks into standard .NET build process (dotnet build/run)
• Custom project template for developer experience

Current capabilities:

• Basic Hello World examples working
• Simple sprite manipulation
• Color palette changes
• Limited method/subroutine support
• No support yet for classes, garbage collection, or complex C# features

Development workflow:

• Write C# code in normal IDE
• Build converts to NES ROM format
• Launches in emulator automatically
• Fast iteration cycle for development

Key technologies used:

• System.Reflection.Metadata for IL parsing
• MSBuild task APIs for build integration
• Native AOT concepts similar to iOS/Android
• 8bitworkshop.com for reference/testing

Main educational value in understanding:

• IL to assembly conversion
• Build system integration
• Retro computing history
• Low-level programming constraints