Malik wrote:

Is the need for the bus card that spelt it's own demise, whereas the PS/2 port preservered?

I'd say this is part of the answer.

For the rest, I don't know for sure. Back when PS/2 became standard IBM was still a pretty big name in computer business (everything had to be IBM compatible 😜).

Perhaps MS bus mouse was proprietary? Or perhaps it was more difficult to implement? I don't know. Maybe check wiki? brb

Edit:wiki has the answer 😉

Is that any relation to the Apple ADB mouse?

Well a big reason must have been the integration into the ATX form factor and PC97 specification. Why bother with another interface card when the specification had PS/2 mouse and keyboard? I'd imagine it's also the reason why serial mice died out too.

I guess electrically and functionally it is similar to a PS/2, minus the card?
(The bus port is not compatible with ps/2 port.)

The drivers - I wonder if ctmouse supports a bus mouse?

A (bus) board dedicated to a mouse sounds like going the extra mile for the mouse. I wonder if the board provided advantages (ignoring the requirement for an isa slot and possibly a more expensive initial investment for the card at that time) over it's serial and ps/2 counterparts. I wonder if more could have been done with the interface card and add extra hardware functionailty on it to add extra features?

(P.S. This is more like a post-mortem review. 😁)