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TonyDuell · 30th Sep 2018, 5:19 pm

No. The XT and AT keyboards had essentially the same pinout, 4 signals (+5V, ground, clock, data). I think the original PC (and XT) had a reset signal (from motherboard to keyboard) on the last pin of the DIN plug but I don't think any keyboard used it.

What was different was the serial communication protocol over the clock and data lines. For one thing the AT one was bidirectional (to control the keyboard LEDs). But there were many other differences too.

But I seem to remember too that the AT would send something to the keyboard at power-on. As a result a keyboard could tell what sort of machine it was connected to. And autoswitching keyboards certainly existed.

30th Sep 2018, 5:19 pm	#3
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,213	Re: Old Keyboard Puzzle. No. The XT and AT keyboards had essentially the same pinout, 4 signals (+5V, ground, clock, data). I think the original PC (and XT) had a reset signal (from motherboard to keyboard) on the last pin of the DIN plug but I don't think any keyboard used it. What was different was the serial communication protocol over the clock and data lines. For one thing the AT one was bidirectional (to control the keyboard LEDs). But there were many other differences too. But I seem to remember too that the AT would send something to the keyboard at power-on. As a result a keyboard could tell what sort of machine it was connected to. And autoswitching keyboards certainly existed.