wrote:
On Sun, 9 Dec 2018 11:39:39 -0500, John McGaw wrote:

On 12/9/2018 10:43 AM, wrote:
I am trying to fire up this W7 PC to eventually use on a PS/2 KVM. The
PC has only one PS/2 connection (plus a few USBs of course). I want
to use a keyboard and a mouse which both are PS/2. I tried using both
the keyboard and mouse one at a time and both work during bootup. So
they both seem to work. Even in W7 altho still only one at a time.
I have to make things work with both mouse and keyboard connect of
course. I then tried using both connected to a Y connector which
changes the connections to the single PC USB input connection. Both
mouse and keyboard still work during boot. However, when I get to W7,
neither work. Funny, since both work when alone. Even when using the
Y connector. So the mouse, keyboard, Y connector, and PC USB port all
seem to be good individually, but not together, which I seem to need.

aarrrggghhhhh!

???

I hope someone can tell me what to try.
Al

No guarantees:

https://www.amazon.com/StarTech-Keyb...dp/B000067SLZ/

There are cheaper alternatives availlble.


That looks like mine except the white end on my 'y' is USB. Are you
saying that reducing the keyboard and mouse PS/2 connectors down to
one PC/2 connector will work when mine won't? That wud mean the
problem is in the conversion from PS/2 to USB wouldn't it?
Al

There are two adapters.

John is showing your the PS/2 splitter. It's passive and
just a rewiring job in effect. The PS/2 on your PC, has
enough wires on it to run two connectors... if that's how
they wired it on the motherboard. If the motherboard end
isn't the right type, the PS/2 splitter only works on
one port. The mouse CLK/DATA are wired to one connector,
the keyboard CLK/DATA are wired to the second connector.
Power and GND are wired as you would expect.

PS/2 (6 pins) -------- PS/2 4 pins get wired as normal
\________ PS/2 4 pins get wired as normal

There is a tiny reference in the comments of the pinout diagram
here. It tells you how the motherboard end can be using all
six pins, to house two interface sets.

https://en.wikipedia.org/wiki/PS/2_port

Pin 1 +DATA Data
Pin 2 Not connected [b]
Pin 3 GND Ground
Pin 4 Vcc +5 V DC at 275 mA
Pin 5 +CLK Clock
Pin 6 Not connected [c]

[b] Sometimes, keyboard Data for splitter cable
[c] Sometimes, keyboard Clock for splitter cable

*******

The other kind of adapter for PCs, is an active adapter
that converts a USB port to two PS/2 ports.

USB ------- 8 bit micro ----------- PS/2 mouse
inside plastic ------ PS/2 keyboard
blob

Those rely on a fixed firmware the 8 bit micro runs,
to convert PS/2 serial protocol, into USB packets.
Usually on the order of $10 to $12 or so. At one point,
that micro went out of production, so it's hard to say
which chip they use today.

Paul