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Thread: AT compact clone - 384k + RTC card just caught fire - what do?

  1. #11
    Join Date
    May 2017
    San Jose, CA USA


    Nice RTC... mind if I Xerox it?

    2018-10-16 16_08_19-Window.jpg

    First time creating an ISA card. Thankfully DipTrace had an 8-bit ISA card template in its Patterns library. Had to recreate/estimate some of the traces hidden under chips, but I'm pretty sure this is exactly right.

    Nearing the end of the quick little project, though, I realized this may not be the best solution, as RTCs don't generally have adjustable address settings, and I think the later PCs standardized on a different controller chip, so this one may need some obscure driver to run in autoexec.bat every time.

    May be time to ask the broader forum for feedback on how to best implement an original PC-compatible modern RTC chip. Guessing the BIOS of more modern PCs handles the RTC functions, so that would be "out", but it also opens up the ability to use whatever RTC chip we want - since the BIOS doesn't have support for RTC. Maybe a tiny option ROM?

    I want to get something built to send over to lo-tech to be integrated into the RAM card. It's a perfect marriage and creates the uber-essential RTC+RAM card that everyone seemed to have back in the era.

  2. #12


    My advice is: don't bother with the RTC.
    RTC needs battery to work, and it's better not to have any battery in a vintage box.
    If you don't like entering date/time manually, you can install a NIC and get time via the net, and having a NIC helps with other things as well...

  3. #13
    Join Date
    Oct 2016
    Cincinnati, Ohio USA


    I have an XT-Turbo PC that has a multifunction card that provides Floppy, serial, parallel, and game ports plus a RTC powered by a coin cell battery. The computer is a DTK and I think the card is also. Try doing eBay and Amazon searches for 8 bit multifunction cards. I think it is this one:!45231!US!-1

    With one of these and the Lo-Tech 1MB board you would be all set.
    PCjr, DTK PC-XT Turbo, 386DX 33, 486 laptop, Pentium 120, Pentium III 500, various old laptops, Commodore Colt, all working. I also have a 286 that I need to see if I can repair.


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