At least PS/2 cables were mostly made with "keyed" rubber jackets where one side was flat and the other rounded, so in the dark you could tell which way was up.
(Though, that keyboard and mouse were different ports was stupid, so it loses points there)
Never have I been able to successfully plug a PS/2 port in by haptics alone.
I can totally see how they were designed to theoretically allow for it; practically, the tactile feedback for the correct orientation is just way too subtle.
And regarding the two different ports: I can't remember (or rather, I was never motivated to revisit the plugs once connected to experiment, since it was such a pain) – was there a technical reason for that, or could modern mainboards/BIOSes/OSes detect and correct for that?
> was there a technical reason for that, or could modern mainboards/BIOSes/OSes detect and correct for that?
IIRC, there was a technical reason in that original mainboards lacked the circuitry to detect and correct for it (I think different mouse vs keyboard interrupts were involved?), and it would have been a extra x¢ on the BOM. But modern mainboards just use two of the same circuit and in fact do work fine if you swap them (tested just now, sample size of 1).
PS/2 connectors were a regression on AT DIN & D sub 9-pin serial for most practical purposes.
The only upside of PS/2 was a higher mouse data rate, particularly with high monitor refresh rates, made mouse movement smoother. You didn't get this for free in Windows though, you needed a registry tweak to tell the mouse driver to bump the sample rate.
The huge downside was that PS/2 peripherals couldn't be inserted when the PC is turned on. They need to be inserted at boot time, and aren't detected if they're plugged in later.
And the keyboard and mouse connectors were physically the same but not generally switchable.
The fact that keyboard and mouse connectors in ps/2 were not interchangeable was really annoying. No matter how much USB-A is annoying, this alone made having USB keyboards and mice a win in my book.
Keyboard was always the one closest to the mobo, since it was there first (and was originally a larger, more robust DIN connector); the mouse piggybacked on top of that later.
(Though, that keyboard and mouse were different ports was stupid, so it loses points there)