ChatGPT on a Psion 5MX, because why not?

A thoroughly unnecessary RetroModem upgrade: ChatGPT on a Psion 5MX, complete with web search and a few carefully limited network-agent tools.

Björn

26 Oct 2026 • 1 min read

After adding IrDA and a web interface to RetroModem, I showed the project to a friend on Signal. Mostly as a joke, he suggested adding ChatGPT to the dial-up BBS.

Challenge accepted.

You can now dial 5559999 from a Psion 5MX to connect directly to ChatGPT through RetroModem. There is no menu to navigate. As soon as the connection is established, you can start chatting. It is all plain text, which works surprisingly well on an old handheld.

ChatGPT login is handled through the RetroModem web interface. From there you can also choose whether conversations should continue where you left off and enable or disable the agent functions. ChatGPT can use web search when it needs recent information.

ChatGPT running as a dial-up BBS on a Psion 5MX, showing a successful ping of the local router through RetroModem — ChatGPT on my Psion 5MX, checking if the router is still alive.

I gave it a small and intentionally limited set of network tools. In the screenshot I ask it to ping my router. Three packets are sent and the result appears directly in the conversation. The agent functions can be switched off completely from the web interface when they are not needed.

Of course, opening ChatGPT on my phone would be faster and considerably easier. But where is the fun in that? My Psion can now talk to an AI and ask it to ping my router, so I consider the experiment a success.