dbreunig/nesformer
A developer baked a working NES 6502 CPU emulator into Qwen3.5-4B model weights
“I think we should build it! Just for fun. It's okay if it's not fast. We want to be able to have the weights, and a cli to run them that we can point at a ROM.”
Drew Breunig embedded a functional NES 6502 CPU emulator into the weights of Qwen3.5-4B, enabling playback of NES ROMs like Super Mario Bros directly inside the model. This builds on earlier work by Divyansh Agrawal and demonstrates an unusual capability: encoding computational state machines into transformer weights. While a creative proof-of-concept, it highlights the growing frontier of encoding deterministic computation into LLM weights.