dbreunig/nesformer
Simon Willison’s Weblog
Newsletter
30th October 2026 - Link Blog
dbreunig/nesformer (via) Inspired by qwenputer by Divyansh Agrawal, Drew Breunig baked a working emulator for a Nintendo Entertainment System 6502 CPU into the weights of Qwen3.5-4B. You can now play NES ROMs such as Super Mario Bros (very slowly) running inside Qwen!
In a comment on Hacker News Drew reveals the Opus 5.5 prompts he used to build this system:
Read this article and any relevant source code: https://divagr.com/blog/qwenputer. Then explore if you could emulate the chip and ram in a Nintendo Entertainment System (as people do today with FPGAs in MISTRs) using this technique. If so, what size model would you have to build and if you could use smaller faster ones, could you get it to be at the standard clockspeed.
Followed by:
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.
Apparently Opus found and then used this collection of conformance tests for the NES CPU released 15 years ago by Christopher Pow.
Recent articles
The October inflection point for vibe game development - 28th October 2026
Battle Drones - a vibe coded RTS with audio-based multiplayer - 20th October 2026
Hello Python 3.15, goodbye 3.10, and now I can use 3.11 - 12th October 2026
A new feature for my blog, built using my voice - 9th October 2026
This is a link post by Simon Willison, posted on 30th October 2026.
games 26
ai 2,304
generative-ai 2,044
llms 2,009
drew-breunig 22
qwen 63
conformance-suites 12
Monthly briefing
Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.
Pay me to send you less!
Sponsor & subscribe
Disclosures
Colophon
©
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026