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Thread: Compaq Portable III - Keyboard Controller

  1. #1
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    Default Compaq Portable III - Keyboard Controller

    So, I got this Compaq Portable III (386DX20), which was basically in pieces, because the previous owner tried to fix a crumbled keyboard cable. I think he forgot to write down the wire colors on the DIN5 connector before trying to replace the cable, because when I got it, each of the 4 wires was soldered to a metal pin. So I think he got tired and started to stick the pins in different combinations into the DIN5 port on the Portable III. It seems that while doing that, he blew something on the system board. I already replaced the keyboard controller chip (Intel 106436-001) on the board, as it got quite hot to the touch, but I'm still getting a 301/304 Keyboard Error in Post.

    Now I have some questions. Has somebody tried to connect a normal AT DIN5 or PS/2 keyboard to a Portable III? If I use the original Compaq Keyboard, I'm getting constant buffer beeps while the 301/304 error is on screen, the same with a PS/2 keyboard. The Compaqs keyboard on another Pentium 133 system instead, works perfectly.

    I wasn't able to track down any kind of schematic for this machine, or any other Compaq that uses the Intel 106436-001 as keyboard controller (there are quite a few), neither could I find the pinout for the Compaq Portable III's DIN5 connector, but I would assume that it's AT standard for 5V/GND/CLK/DATA, maybe someone could confirm this for me?

    Any help would be greatly appreciated.

  2. #2
    Join Date
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    Quote Originally Posted by Soeren Anton View Post
    I already replaced the keyboard controller chip (Intel 106436-001) on the board, ...
    Not an Intel part number; a Compaq one. The "106436-001" is an Intel D8742 (multipurpose microcontroller) chip that Compaq have programmed with software that turns it into a 'keyboard controller' suitable for the Compaq motherboards where it gets fitted. Compaq have then assigned its part number of 106436-001 to that particular combination of hardware and software.

    Hopefully, the "106436-001" that you acquired is programmed.



  3. #3
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    In the IBM AT, IBM have also used a programmed 8742 (or 8042). For whatever it is worth, the keyboard interface of the IBM AT's motherboard is shown at [here]. Compaq may have done something very similar. Note the chips between the controller and keyboard connector.

  4. #4
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    Jun 2014
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    That's actually some pretty good insight, thank you. I didn't know that the 106436-001 is actually a D8742, the original controller wasn't marked like the one in your picture. I found some NOS 106436-001 from a seller in Poland, they were actually dirt cheap, too.

    snip_20180608161811.jpg

    I was hoping that there was something between the controller and the connector to go on, but without the schematics I was a bit lost on this board, as the chip density is pretty high. I think the next step is to trace the DATA and CLOCK lines from the connector to pins 37 and 38 on the controller, something in between there must be screwed.

  5. #5
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    Quote Originally Posted by modem7 View Post
    For whatever it is worth, the keyboard interface of the IBM AT's motherboard is shown at [here].
    A related diagram is at [here].

  6. #6
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    Do you have any information about the hard disk controller? That seems to be a custom Compaq-fabricated chip that doesn't exist anywhere else.

    (My hard drive controller failed a few months ago, and I haven't been able to restore it to fully-working condition yet.)

  7. #7

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    Unfortunately - no idea about the HDD controller - but my first thought was like "this is a case for XTIDE". Not a perfect solution, but maybe worth considering if you can't get the controller fixed.

  8. #8
    Join Date
    May 2016
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    Fairfield, Ohio
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    If memory serves that unit actually uses an IDE drive.

    BTW, an actual Portable III has a 286 cpu. The 386 systems is called, well, Portable 386.

    Given that I've never taken either one apart (aside from replacing a floppy drive once), I am surprised to read the system has an internal DIN5 keyboard connector. Surprise!

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