Drew Breunig Embeds a Working NES 6502 Emulator Inside Qwen3.5‑4B

On 30 October 2026, Drew Breunig announced that he has integrated a functional Nintendo Entertainment System (NES) 6502 CPU emulator into the weight matrix of the Qwen3.5‑4B language model. The emulator can run NES ROMs—including a very slow version of Super Mario Bros—directly within the model’s inference engine. Breunig revealed the Opus 5.5 prompts he used to construct the system and cited the 15‑year‑old conformance test suite from Christopher Pow as a key resource. The project demonstrates that large language models can host low‑level hardware emulation logic, opening a new avenue for embedding executable code within neural network weights.