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Thread: Intel 8021 for Mac keyboard M0110

  1. Default Intel 8021 for Mac keyboard M0110

    Through the controlled processes of troubleshooting I have determined that the Intel P8021H 2173 chip in my M0110 keyboard has failed. Date code: 8404. Can anyone supply me with a replacement?

  2. #2
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    The part number is "P8021H". The "2173" is the date code, meaning the chip was manufactured on the 21st week of 1973.

    Unfortunately, unless you can find the exact same model of keyboard and pull the 8021 off of it, replacing it won't help you.

    The 8021 is an i8048 MCU with integrated mask ROM. Unless you have another 8021 which happens to be programmed with the exact same code as the existing chip, it won't work.

    There are numerous ways to fix the problem by substituting the 8021 with another similar MCU and external ROM, like an 8051; But not only would this be expensive, it also requires extensive knowledge of MCUs, assembly language, logic analysis and E/EPROM programming. It would be simpler to just buy another M0110 keyboard off Ebay in rough condition and just swap the PCB out to your keyboard.

  3. #3
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    A mask programmed processor for a Mac keyboard made in 1973 would be a miracle, the Mac wasn't designed until 1983.

    Tom

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    Well, how desperate are you?

    See this thread

    Yes, I just checked, the Philips/NXP MAB8401B has identical pinout to the Intel 8021H and has a top-mounted "piggyback" socket to accept either a 2732 or 2764 EPROM.

    According to the cited thread, the MESS archive may indeed have the microcontroller firmware available.

    The combination will be taller than the original 8021H, but should work otherwise.

  5. Default

    Maybe Al Kossow has a spare.

  6. #6
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    Quote Originally Posted by hornbetw View Post
    A mask programmed processor for a Mac keyboard made in 1973 would be a miracle, the Mac wasn't designed until 1983.

    Tom
    I did a bit of further digging and apparently there were some 8021s with an EPROM instead of a mask ROM, so the date code would make sense. It was a bit of a head scratcher for me as well.

    Since the 8021 doesn't have a window, the EPROM could only be programmed once, unless you wanted to get dangerous with fuming nitric acid.

  7. #7

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    Intel's date codes do not show the date directly. These are more like run numbers. For each product, you'd need to have a list for that product to determine what date the code matched. The part was likely made within a couple months of the rest of the parts in the Mac. Most of the TTL parts have a date code showing year and month. The 8021 code is not a direct date code.
    In 1973, they had just made the 8008 and were finishing the 8080 design. The 4004 was the main product of that year. The 8048 and 8021 were still on the minds of the designers at that time.
    Dwight

  8. Default

    Everyone: I am most interested in sourcing a replacement part. Less interested in codes and markings.

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