Devonshire wrote:

OTOH, my first computer was a PDP 11/45 (?) which only had paddles and
blinking lights.


You don't know that. Why do you assume that the only thing I knew
about was IBM compatables? My first computer was a Commodore Vic-20.
It wasn't IBM compatable, nor did it come with an "optical mouse".
Which means absolutely nothing.

Well, if you had a brain, then you would have realised that I was
blinkered to that possibility, but in any case it was after PDP's. The
point of the post was that optical mice existed well before they made
the ibm-compatible stage.