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Thread: IBM PCjr extras identification help

  1. #1

    Default IBM PCjr extras identification help

    i recently picked up a PCjr system from a local guy. it works great and came with tons of software and accessories.

    can anybody tell me what the attached are, specifically the three black dongles bottom right. i though he said they were diagnostic tools of some type. the connectors match the various rear connectors on the jr.

    also, the cards. i'm assuming RAM?

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  2. #2
    Join Date
    Mar 2011
    Atlanta, GA, USA


    The cards are the stock internal cards from the unit. The bottom card is the internal 64K to 128K RAM expansion. It goes in the 2nd slot from the left when looking at the front of the machine. The top card is the internal floppy disk controller. It goes in the far right slot when looking at the front of the machine and the cable connects over the top of the card.

    The 3 plugs are from the PCjr maintenance manual. They are loop-back plugs for testing serial port, joystick, keyboard, and light pen ports. There is an internal diagnostic routine in BIOS that uses them.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  3. #3


    thank you!


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