Plug keyboard into PS/2 mouse connector
Andrew Henderson 
Hi!
I have two PS/2 keyboards and USB mice. So i want both keyboards plug into PS/2 ports. But how can i force Win XP (Prof. SP2) to recognize keyboard in PS/2 mouse connector? (Green one). I don't want to buy PS/2 to USB convertor. Why would i do that, when i have two PS/2 ports? =).
THX for your help =).
04 Answers
Most computers will not recognize a PS/2 device when it's plugged in the PS/2 port for the other device. So you usually cannot plug a PS/2 keyboard in a PS/2 mouse connector, or vice-versa.
You'll find more information on the PS/2 connector page on Wikipedia:
The design decision for identical but incompatible connectors would prove aggravating to consumers. To help alleviate this, PS/2 keyboard and mouse connectors were later color-coded: purple for keyboards and green for mice as defined by the PC 97 standard.
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The pinouts of the connectors are the same, but most computers will not recognize devices connected to the wrong connector.
It depends on the motherboard. Reaching way back in my memory here, but I seem to recall that older computers you could put either type of device in either port as both ports were always fully wired up (If I can find my old PS/2 hardware book I'll verify it, but I'm pretty certain mouse and keyboard use different data lines). I seem to recall that at some point the manufacturers started cutting costs by not fully wiring both ports, thereby making one keyboard only and one mouse only.
You could hack it electronically, both PS/2 and USB use the same 4 inputs/outputs: Voltage, Ground, Clock, Data. The problem is that there's no universally accepted pin layout, which is why PS/2 to USB connectors don't work unless the keyboard supports USB as well anyhow, hence the need for fancy PS/2 to USB adapters.
If you have an old keyboard like say an IBM Model M, the electronics and pins inside it are well documented so you should be able to accomplish it with few problems. However you'd have to get some fancy footwork on the go with a soldering iron depending on your motherboard if you want to make the green PS/2 port working with a keyboard.
One way to do it, if you wanted two keyboards at once as I do, is to unsolder that green port and connect it pin for pin to the purple one - that's what I'm gonna do, although I'm doing it slightly differently - sticking the port in the back of my UNICOMP Terminal Emulator and wiring the 4 pins up on the circuit board so I can plug my IBM Model M into it :D
~ All must bow before "the one true keyboard" and its perfect, super-sonic buckling spring design! ~ Rob ~
It's not clear whether you want to plug both keyboards in at the same time, and what you would do with the mouse(s).
In any case, I'm sure I've noticed in the past that it sometimes doesn't matter which PS/2 connector I use for the keyboard and mouse - the OS realises which is which. I think this happened on one motherboard, at least.
Presumably, though, the OS expects to find just one keyboard. I would expect it to ignore a second keyboard, even if it were possible to connect it.
