Figuring out a Japanese-exclusive IBM P/N 69H8533 numeric keypad

Hey, all!

About a year ago, I picked up this cool-looking IBM numeric keypad from Yahoo! JAPAN Auction, going into the purchase fairly blind since there’s barely any information about it available online. When it arrived, it turned out that whilst it had a PS/2 plug, it wasn’t working with any ports or active converters I tried. As such, starting two days ago, I finally decided to rectify the lack of information surrounding this keypad.
Here’s my latest article about it, including details on its host system and its interface:

As a TLDR; it’s indeed AT-compatible, but it’s got a custom PS/2 pinout. I’ve created a diagram (computer-side/female view) below for anyone interested. What IBM did was combine the connections for the keypad and the PS/2 mouse pass-through port through one PS/2 plug, but, they made the mouse component of this connection take up the ‘dominant’ pin positions expected by a standard PS/2 port. As such, only the mouse pass-through port works if you hook this up through the relevant standard PS/2 port. But with the pinout below, I was able to wire up a Teensy 2 specifically for it and it indeed works! As an extension of this project, I’m also investigating a few ThinkPad numeric keypads that have PS/2 mouse pass-throughs since I’ve already found an example that uses the same pinout.

To be honest, its switches are nothing special, but it’s certainly not unusable. And besides, if this helps someone repurpose this old tech and saves it from the landfill, I’m happy. It’s cool, functional (the extra keys it has are genuinely useful), and IBM; so it’s good enough for me! For those curious, there’s still some for sale on Yahoo! JAPAN Auction.

Anyway, hope the article is an interesting read. Cheers!