24 Sep
2011
24 Sep
'11
7:11 p.m.
On 24 September 2011 18:43, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Firstly, no, it was not just for PS/2s; fairly soon after the PS/2,
other machines took it, and a few years later, /all/ PCs used the same
connector.
Secondly, yes, the interfaces were close enough to the same that some
BIOSes would actually display an error message saying "mouse inserted
into keyboard port" or /vice versa/. Helpful but not as helpful as
just bloody working with it, whatever socket it was in, would have
been.
No, instead, for a decade and a half or so, keyboard sockets were
coloured green and so were the plugs, and mice in matching purple. (Or
possibly the other way round. I don't use such modern keyboards. :?) )
But finally, in the last few years, you get sockets coloured half
green and half purple, and either a mouse or a keyboard will work in
it - or if the PC has two, either will work in either port.
So they are close enough to be interchangeable - finally. No, that
doesn't mean the signalling is the same, but it means they are
electronically close enough to be swapped over, and that a smart
enough BIOS could detect which type of device was attached.
I never said there was. Just nobody did it. It was part of the PS/2
spec from the beginning and became an industry standard.
--
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I have no clue about the signalling level stuff, but there were also
PS/2 mice; same physical socket, different signalling. Mice wouldn't
work on keyboard ports and keyboards wouldn't work on mouse ports,
until the very end of the lifetime of the standard.
Hang on a second. Logically, a 'PS/2 keybaord' is one that works on a
PS/2 computer. A PS/2 mouse is simularly one that works on a PS/2
computer. There is no reason to assume that the interfaces must be similar. There were
never AT-interface mice - so *something* in there is different.
Only because no PC/AT keybaord interface microcontroller exepcted to talk
to a mouse. There is nothing to stop them existing.