NKRO on old keyboards

[elecplus]

Yesterday a young man came to my warehouse and spent about 3 hours testing out the feel and function of quite a few old keyboards. He is fairly new to the hobby, but he tried out about 12 different keyboards. Much to his delight, he found quite a few that met his requirements of being able to hit Alt+ Crtl+x on most of the older boards, including a Wyse PCE, an Everex with clicky black Space Invaders, and an old 83086 era keyboard with white Alps. None of these are advertised with these capabilities, so we were pleasantly surprised. We did not try anything more complicated, but almost any 3 key combination seemed to work fine. We used Orihalcon cables to connect to a Windows 7 computer with USB.

[amigastar23]

I bought an
ARC-Monterey-K102-K101-ISO-vintage-keyboard-SKCM-White-Alps
i wonder if it will support Nkro over PS/2. But probably not

[fohat]

being able to hit Alt+ Crtl+x

That is my keyboard shortcut for the weather report, and as well as I can remember it has worked on every keyboard that I have tried, including Model Ms and any of my laptops. Presumably there were more difficult tests.

[xxhellfirexx]

I thought modifier keys do not usually count in the NKRO limit.

[kmnov2017]

You can press (and register) ctrl alt X on any keyboard ever made ...

[Findecanor]

IBM and later Microsoft have issued specifications of which key combinations that PC keyboards are required to support. These include combinations of any two (types of) modifier keys plus one alphanumeric key. (Two modifiers of the same type are not required to work)
Microsoft expanded on IBM's spec with the Windows keys and to require combos with even more keys, including Enter.

I'd think that other platforms have had similar specifications. I've seen that Apple and Commodore have had keyboards where each (type of) modifier key has been on a dedicated pin to the microcontroller to ensure these combos. The Commodore Amiga even had a standard keyboard matrix.

[TheInverseKey]

@elecplus Most terminal terminal keyboards that are WYSE or rebanded are NKRO. Also some space invader boards are as well but they have to have the diodes in order for this to be applicable.

[Inxie]

Here's an IBM Model F keyboard from the original 1981 PC.

https://streamable.com/pun5hq

Demonstrating even the original PC keyboard had NKRO.