Old IBM keyboards - Page 3

Originally Posted by Bear

But what does the at plug in to ??? : D

Okay, the jack labeled "system connector" plugs into the computer. That's a PS/2 connector.
The jack labeled "keyboard connector" plugs into the keyboard.


The "system connector" can either be a PS/2 connector (mini-DIN), or an AT connector (DIN). The SDL "keyboard connector" end always stays the same.

Both AT and PS/2 are essentially the same connector, just using different DIN jacks. This end always plugs into your computer. Older computers like the 5170 use AT. Whereas computers like a Personal System/2 model 9595 will use the smaller mini-DIN PS/2 jack.

For example, someone here has a model F AT with an AT to PS/2 adapter to use it in a regular PS/2 port:




If you take off the adapter, then you can plug it into an IBM 5170, you'll see a big circular jack to the left of the I/O panels:

Originally Posted by Bear

wait. the networking type connector is on both ends of these older keyboards. There is no PS2 connector included???

It goes from SDL to PS/2, as pictured here:


SDL end plugs into the keyboard. SDL is actually better shielded than RJ45, and has two little notches, not too unlike a USB connector:

I'm not trying to single you out 89, I was only hoping you might know what these connectors were originally developed to plug in to : )

Originally Posted by Bear

I'm not trying to single you out 89, I was only hoping you might know what these connectors were originally developed to plug in to : )

The AT protocol was first released on the IBM 5170s (pictured above). It doesn't matter if it uses a mini-DIN or DIN connector-- it's all the same. But yeah, the first computer to use AT would be the 5170.

What I'm wishing we knew, is what was that connector originally designed to plug in to? I just don't see how it could possibly have been designed to plug to a PS2 adapter, else why wouldn't it simply been produced WITH a PS2 plug on it?
what is that connector originally supposed to plug in to ?

Originally Posted by Bear

What I'm wishing we knew, is what was that connector originally designed to plug in to? I just don't see how it could possibly have been designed to plug to a PS2 adapter, else why wouldn't it simply been produced WITH a PS2 plug on it?
what is that connector originally supposed to plug in to ?

It was designed for the IBM 5170 keyboard jack. The IBM 5150 used it too but with a different protocol.

Later in the Personal System/2 series IBM shrunk the connector the a mini-DIN.

is it an add in card that supports it maybe ? was the original plug built into the computer, or was it on an add in card ?

Originally Posted by Bear

is it an add in card that supports it maybe ? was the original plug built into the computer, or was it on an add in card ?

The AT plugs were physical jacks on the systemboard-- starting on the IBM 5170, and many PC clones.
Here's a photo of a generic 486 board with an AT female jack for an AT keyboard:

i'm getting a photo together here 89. My connection a terribly slow one, working on a photo tho : )

Originally Posted by Bear

here it is, why is no PS2 in sight? what was this connector designed to plug in to ? : ) thanks for any insight (no pun intended) I've seen scores of this type of keyboard connector, with never a clue what it was designed for

Well before "AT" was downscaled to mini-DIN, all computers used the larger 5-pin DIN plug for the keyboard jack. Hence the reason for the different cables and adatpers: earlier computers use AT, later computers use PS/2.
AT = 5 pin DIN (found on early computers starting with the IBM 5170)
PS/2 = 6 pin mini-DIN (found on later computers-- presumably starting in 1987)

Both AT and PS/2 use the same protocol for communication.

but what the flying hell does it plug in to ?

Originally Posted by Bear

but what the flying hell does it plug in to ?

Plugs into the computer (it's on the motherboard). The first computer to use it was the IBM 5170. That's why a lot of older computers have the large 5-pin DIN jacks on the back.

What's the part number on the keyboard? I believe this is for a terminal, not a PC.

imgbox - fast, simple image host

Yes, that is a terminal keyboard. It's not PC-compatible. To the best of my knowledge, there is no commercially available converter for it, although people have come up with various hacks to get this model to work with PCs and Macs. It's kind of a PITA to get it to work, apparently. (I personally have never tried, but if you're really interested, see this link, for example: XT/AT/PS2/Terminal to USB Converter with NKRO • deskthority.)

A good quick reference for the confusing array of "Model M" keyboards is available at Model M keyboard - Wikipedia, the free encyclopedia.
(To see the chart, be sure to press the "[show]" link in the "Part Number" header cell.)

I've searched many times for clues to what those connect to and never got even a hint. A lot of information on the connector, but never anything on the connection/connecting point. Seems I was using the wrong search terms, i.e. "connecting ibm to computer", etc.
Anyway, thanks for the help. I searched the part number and found an interesting thread on this type of board
What Can I Do With a Terminal Model M?
Now it all kinda makes some sense.