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No mouse? and Serial port pinout discrepancies

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First post, by tpowell.ca

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Hello everyone,
So I discovered something today while trying to get a serial mouse working on my 486.
It would seem that older machines with serial port headers differed from the pentium era and up.

Basically, I thought I was losing my mind when all I was unable to get any serial ports working unless I used add-on serial cards.
I assumed the motherboards had a faulty UARTS ships, but after a 3rd motherboard, I figured something was wrong.

Ok, so here is how its different:
On most pre-Pentium (AT spec?) systems, the ribbon cable is wired as shown.

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Last edited by tpowell.ca on 2018-02-11, 03:15. Edited 1 time in total.
  • Merlin: MS-4144, AMD5x86-160 32MB, 16GB CF, ZIP100, Orpheus, GUS, S3 VirgeGX 2MB
    Tesla: GA-6BXC, VIA C3 Ezra-T, 256MB, 120GB SATA, YMF744, GUSpnp, Quadro2
    Newton: K6XV3+/66, AMD K6-III+500, 256MB, 32GB SSD, AWE32, Voodoo3

Reply 1 of 4, by tpowell.ca

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I hope this helps some of you to fix/resolder new serial port slot adapters to work on old machines.

Last edited by tpowell.ca on 2018-02-14, 22:51. Edited 1 time in total.
  • Merlin: MS-4144, AMD5x86-160 32MB, 16GB CF, ZIP100, Orpheus, GUS, S3 VirgeGX 2MB
    Tesla: GA-6BXC, VIA C3 Ezra-T, 256MB, 120GB SATA, YMF744, GUSpnp, Quadro2
    Newton: K6XV3+/66, AMD K6-III+500, 256MB, 32GB SSD, AWE32, Voodoo3

Reply 2 of 4, by Jo22

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Yes, that's good to know - thank you for sharing your discovery with us. 😀

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 4, by Cyberdyne

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That i know, but i think there are also porblem with old LPT connectors, because, some old AT motherboards LPT do not work with modern plugs, i tested the grounds and they are the same, only no key, so the standard key is also GND. And last pin, what is also GND, is not GND in those. But all the other pins are mystery. LPT DAC is silent. So something is wrong. And it is problem with those first generation 486 AT integrated motherboards.

I am aroused about any X86 motherboard that has full functional ISA slot. I think i have problem. Not really into that original (Turbo) XT,286,386 and CGA/EGA stuff. So just a DOS nut.
PS. If I upload RAR, it is a 16-bit DOS RAR Version 2.50.

Reply 4 of 4, by Skyscraper

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"The nice thing about standards is that you have so many to choose from."

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Older PC: K6-3+ 400@600MHz, PC-Chips M577, 256MB SDRAM, AWE64, Voodoo Banshee.

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