VOGONS


First post, by Erwin_Br

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I have bought a “modern” serial cable, with 2 10 pin IDC connectors and 2 DB9 ports. The idea is to connect it to my recently acquired 486 motherboard, a 486-GIO-VT.

Now I just learned that there is no definitive standard for these things and that the pin layout on the motherboard headers might not match the cable. Even worse, I might be able to destroy my motherboard in the process of trying.

Is this true? How big is the risk that I fry my motherboard?

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Reply 2 of 8, by GigAHerZ

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There are two types of wirings - staggered or sequential.

On the external port side, when you lift away the plastic, you can see two types of wirings:
12345
6789
OR
13579
2468

And one fits with your board and other doesn't. To confirm, which way you need it to be, search for the ground pin. That's enough to identify it.

With soldering iron, you can modify the cable easily. 😉

"640K ought to be enough for anybody." - And i intend to get every last bit out of it even after loading every damn driver!

Reply 3 of 8, by Erwin_Br

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My motherboard guide says:
1 - Data carrier detect
2 - Receive data
3 - Transmit data
4 - Data transmit ready
5 - Signal Ground
6 - Ready to receive data
7 - Request to send data
8 - Clear to send
9 - Ring indicator

So the ground pin is number 5 on the motherboard. If I understand correctly, the external cable should then also have pin 5 as ground, but it is possible that it is "mapped" to pin 9 in your example.

Edit: I have measured with a multi-meter, see following post.

Last edited by Erwin_Br on 2021-04-27, 15:30. Edited 1 time in total.

Reply 4 of 8, by Erwin_Br

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Using a multi-meter on the cable itself I was able to measure the layout without having to remove the plastic.

The result:

"10 pin IDC" --> "9 pin d-sub connector"
1 --> 1
2 --> 3
3 --> 5
4 --> 7
5 --> 9
Etc...

So the layout appears to be:
13579
2468

But again, how do I know if that matches my motherboard?

Ground pin is 5 according to the motherboard guide, but what does that mean exactly? My cable's 5 is pin 9 on the d-sub connector. Is that wrong? Should that be also the 5th pin?

Reply 6 of 8, by Erwin_Br

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PARKE wrote on 2021-04-27, 17:36:

This is a 'guide' that shows the difference between the 2 main implementations.
DTK3a.jpg

Thanks! So my cable is clearly the new AT/Everex type, but I don’t know yet my motherboard. I guess I will have to check with the multi meter what is the ground pin.

Reply 8 of 8, by Erwin_Br

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maxtherabbit wrote on 2021-04-27, 23:15:

AT/Everex is vastly more common. I do not believe you pose any risk to the board if it is wrong. Just hook it up and it will 90% just work

Thanks! I will give it a shot.