[snip]

For a while I thought that USB ports did't work until after Windows
started, but PS-2 ports and the larger round ports that preceded them
worked before Windows loaded. As soon as the BIOS ran.

Now I think I'm wrong, but was there ever some truth to this?

I remember one system (from when USB was new) where I connected a PS/2
keyboard for use in BIOS setup. That BIOS didn't use a mouse so USB was
OK for that. It was a few more years before BIOS had USB support. Also,
that old system had only 2 USB ports and I wanted to leave one free for
a USB storage device.

Note that if you're going to use a PS/2 device, it has to be connected
at system boot, unlike USB which can be plugged in anytime.

IIRC, "both" devices (keyboards / mice that work on USB or PS/2) are in
USB mode initially, but switch if they detect a PS/2 initialization from
the PC (which happens only at boot).

--
98 days until the winter celebration (Tue Dec 25, 2018 12:00:00 AM for 1
day).

Mark Lloyd
http://notstupid.us/

"What is the function that a clergyman performs in the world? Answer: he
gets his living by assuring idiots that he can save them from an
imaginary hell." [H. L. Mencken, "Minority Reports"]