I got got hold of an old IBM Model M (Model 1391403, to be precise). Unfortunately, the fixed cable was cut off by an unknown idiot.

enter image description here

Does anyone know what kind of connector (I assume PS/2?) was supposed to be at the other end, and what pins the colors correspond to?

  • 2
    \$\begingroup\$ 5 pin din? Just a guess \$\endgroup\$
    – uglyoldbob
    Jan 22, 2019 at 14:38
  • \$\begingroup\$ You will have to do some reverse engineering. Either find an equivalent board, and check the cable, or try to figure out which pin of the 1.25mm connector maps to the PS2 connector. \$\endgroup\$
    – Lior Bilia
    Jan 22, 2019 at 14:43
  • \$\begingroup\$ They existed with both DIN and mini-DIN/PS2 connector. \$\endgroup\$
    – winny
    Jan 22, 2019 at 14:54
  • 1
    \$\begingroup\$ @winny That's probably the closest thing anyone's going to be able to make to an answer; might as well make it one. \$\endgroup\$
    – Hearth
    Jan 22, 2019 at 15:42
  • \$\begingroup\$ The pinouts of the DIN and mini-DIN plugs are in this post: retrocomputing.stackexchange.com/questions/1132/… You may need to reverse-engineer the colors by careful examining of the board.. I would hope that red=+5V and black=ground, but maybe IBM deliberately didn't do that to confuse people. \$\endgroup\$
    – Simon B
    Jan 22, 2019 at 16:14

2 Answers 2


Here is the pinout you need:

  • +5 V - black
  • data - red
  • clock - yellow
  • ground - white
  • ground/shield - silver

That black as +5 V is not what you would call industry standard and if you salvage a PS/2 (mini-DIN) or DIN cable elsewhere, be sure to match the pinout and not the colors.

Here is a pinout for both DIN and mini-DIN enter image description here

Ready-made cables for the very purpose are sold online too: Cable

(Side note: I wrote in a comment above that it existed with both mini-DIN and DIN. This may have not been 100 % accurate. My old PS/1 (or was ut just called personal system?) came with bucking coil keyboard and PS/2 connector which was very similar but more compact than an actual and original model M.)

  • \$\begingroup\$ Thank you so much! I‘m still waiting for my PS/2 cable to arrive, and I assume it will work with this. (I can’t find the ready-made cables anywhere though, but I assume shipping would be to much of a hassle for me anyway as I’m in Germany.) \$\endgroup\$
    – Fii
    Jan 23, 2019 at 9:11

The TTL IC supply pins are known, ground and 5V. To find out the connector wires, I suggest you use a multimeter to trace ground and 5V supply wires first. After connecting power correctly you can figure out clock and data wires by trying both ways or with an oscilloscope.


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