nesformer Embeds NES Emulator in Qwen3.5-4B Model

Drew Breunig created nesformer, embedding a working 6502 CPU emulator for the Nintendo Entertainment System directly into the weights of Qwen3.5-4B. The system can execute NES games including Super Mario Bros, though with significant performance limitations.

Inspired by qwenputer, Divyansh Agrawal’s earlier work, Breunig used Opus 5.5 prompts to explore whether NES chip and memory emulation could function within neural network weights and whether smaller, faster models could achieve standard clockspeed. The implementation incorporated conformance tests for the NES 6502 processor that Christopher Pow released fifteen years prior.