How to handle a single PS/2 port?

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Nach
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How to handle a single PS/2 port?

Post by Nach »

I have a computer with a motherboard which only has a single PS/2 port on it. It's kind of annoying when you want to use DOS or something else old with no USB support, and want both a keyboard and mouse present.

I see they sell these PS/2 Y Cables (splitters) which allow two PS/2 devices share a single port. But I see lots of people who order these online complain in customer feedback that its incompatible with their motherboard.

Is there any way to know in advance if the motherboard will support one of these? Are these more compact designs just lazy, and the motherboard itself really supports another PS/2 jack connector, if they were both soldered on properly?

Anyone have wisdom on this matter? Thanks.
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odditude
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Re: How to handle a single PS/2 port?

Post by odditude »

Visually, many motherboards will color a dual-purpose PS/2 port half-purple, half-green.

Otherwise, the way to test is to try both a keyboard and a mouse in the port separately. While the connector is physically identical, a keyboard and mouse port are wired differently - the keyboard uses pins 1 & 5, while the mouse uses 2 & 6. (Pins 3 & 4 are Vcc/ground.) If both work separately, then a splitter (which simply shares the power lines and splits the data lines to the appropriate ports) will work just fine.
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Deathlike2
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Re: How to handle a single PS/2 port?

Post by Deathlike2 »

I'm not sure how old this system is, but surely there is some sort of old AT keyboard connection available (strangely, I still have one of those types of keyboards around)? Otherwise serial mice with the proper DOS driver should work...

A PS/2->serial converter (for the mouse) or a PS/2->AT converter (for the keyboard) are the only options offhand that should be available (I'm making some assumptions based on the age of the mobo being pre-USB)... unless the damn thing is a lot more modern... which IIRC most of them should come with (assuming you bought a mobo) some extra brackets that include the other PS/2 connection.
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Nach
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Re: How to handle a single PS/2 port?

Post by Nach »

odditude wrote:Visually, many motherboards will color a dual-purpose PS/2 port half-purple, half-green.

That is indeed the case with mine. That means a splitter should definitely work, and there's nothing else that may conflict?

Is there a particular company I should be getting a splitter from? Or they all basically the same?
I see all these options:
http://www.amazon.com/StarTech-Keyboard ... 529&sr=8-1
http://www.amazon.com/QVS-CC321Y-Keyboa ... 529&sr=8-3
http://www.amazon.com/6In-PS2-Keyboard- ... 529&sr=8-7
http://www.amazon.com/Cables4PC-LAPTOP- ... 29&sr=8-16

I don't think I heard of any of these companies before.
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Deathlike2
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Re: How to handle a single PS/2 port?

Post by Deathlike2 »

The first two links are products from companies that make this type of stuff, like converters and cables (you can get a fair idea of what they are from all the products they sell)... the latter two I have no idea.
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Re: How to handle a single PS/2 port?

Post by Nach »

odditude wrote:While the connector is physically identical, a keyboard and mouse port are wired differently - the keyboard uses pins 1 & 5, while the mouse uses 2 & 6. (Pins 3 & 4 are Vcc/ground.)


Are you sure that's right? Wikipedia has a different story:
http://en.wikipedia.org/wiki/PS/2_connector

Although Wikipedia is a great place for misinformation.

Also, for most motherboards in recent years, I found getting the mouse and keyboard jacks mixed up still worked fine, meaning the motherboard itself must've had everything connected...
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odditude
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Re: How to handle a single PS/2 port?

Post by odditude »

interesting. i guess the "knowledge" i have ONLY applies to splittable ports.

thinking about it further, the wiki info has to be right - a not-uncommon problem i used to get calls about when i worked as a tech was the occasional "spastic" keyboard and mouse after bringing a machine home - because they plugged the keyboard and mouse in the wrong ports. this could only be a problem if the data lines are on the same pin.

sorry for the misinformation. however, it DOES apply to the port on your motherboard.
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Nach
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Re: How to handle a single PS/2 port?

Post by Nach »

Okay, thanks for the help you guys.
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Truth Unknown
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Re: How to handle a single PS/2 port?

Post by Truth Unknown »

If you haven't ordered and still interested in one of those cables, I recommend ordering one from here: http://www.monoprice.com/products/produ ... 1&format=4 If you're worried about the web-site, I've ordered and used enough cables and misc. without fail.
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Re: How to handle a single PS/2 port?

Post by kode54 »

Don't many boards have some legacy USB keyboard and possibly mouse support in the BIOS? While there may not be support for USB mice, there's likely support for USB keyboards in the BIOS, so you can probably just plug in a USB keyboard and use the PS/2 port for your mouse.
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Re: How to handle a single PS/2 port?

Post by Rashidi »

iirc, some dos programs choose to meddling with port $60 directly, and forget using bios/dos interrupt for keyboard purposes.
was legacy USB keyboard bios routine can actually handles such program?
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Re: How to handle a single PS/2 port?

Post by DataPath »

Wikipedia's PS/2 article describes pins 2 and 6 as being "reserved". If you look at their reference for that material, you'll find this:
However, on the NEC Versa 24xx and Panasonic Toughbook CF-35 laptop computers, and some others, there is just one connector on the computer, and it uses "reserved" pins to permit connecting both a mouse and a keyboard via a special "Y-splitter" cable adapter.
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