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Interesting Motorola 68K-like IC?

Discussion in 'Electronic Components' started by mario, Sep 2, 2004.

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  1. mario

    mario Guest

    Dear all,


    I acquired recently a board that looks like an S-100 card, except it has 80
    connectors instead of 100, and was made by tandy.

    So, this board has, among other things, an IC that looks a lot like
    theMotorola 68000 (64 CERDIP, 900 mils wide) and in fact, it sports the
    Motorola logo, but this is what is written on it:

    8040000
    SC88019L
    GN78302

    I also got another board which appears to be some kind of memory card, but
    again, the RAM ICs are some really strange beast: 16 pin CERDIP parts from
    Motorola, with the following text:

    8040665
    BQD8346 (this number varies, as well as the first letter can be an "A")

    These are intermingled with similar-looking ICs which however have the text:

    MCM6665AL20
    FQD8416 (this number varies)


    I don't know what kind of bus do these cards plug into. Maybe a TRS-80?


    many thanks in advance for any hint!


    mario
     
  2. Mark (UK)

    Mark (UK) Guest

    Hi!

    Well, MCM6665 is a DRAM, 4164 equivalent I think (or maybe 4116, my head
    is spinning now...)

    Yours, Mark.
     
  3. Franc Zabkar

    Franc Zabkar Guest

    This site ...

    http://www.vintagefunworld.com/items.asp?ID=14

    .... claims this part is equivalent to a standard 4164 DRAM.
    My Motorola Master Selection Guide (1984) lists this as a 65Kx1,
    200nsec DRAM, probably equivalent to a 4164. Yes, it does say "65K",
    but I guess that's a typo.
    That's a YYWW date code.
    "8040665" appears to be a Tandy part number. I suspect 8040000 is
    also.

    At least one web site states that the 8040665 was a "TANDY Original
    Dynamic Ram Memory IC used in the earlier Tandy TRS-80 and Color
    Computers (CoCo)".


    - Franc Zabkar
     
  4. mario

    mario Guest

    Dear Franc,


    read answers below:

    Yes, so it seems. I guess it would help if I coud find a really good Tandy
    website/resource.
    It should be equivalent to a 4164. The two ICs were randomly "mixed"
    together, serving apparently identical functions. The reason I listed them
    both is, I was hoping someone would recognize at least one of them. Tactic
    which apparently worked.
    I knew that, I just wanted to specify it for completeness (avoid questions
    like "are you sure you didn't just copy the date of production?").
    I am more inclined now than before reading your post, to think the 8040000
    is a Moto 68K, under another name.

    Now, it remains to be seen which TRS computer was so advanced to accept such
    a CPU.


    Many thanks for your help!!!


    mario
     
  5. If it's really a Tandy board, given the date codes it likely is a 68000.
    (My first thought was that it wsa Motorola's first attempt at something
    better than the 68000, which was the 88000 series, but that came later.)

    Radio Shack had a couple of 68000 based computers in the early eighties.
    They weren't intended for the home user, too expensive, but they did
    run Xenix, a Unix variant. One model was like a retrofit on one of the Z-80
    based models, while the other was a standalone.

    Ask in comp.sys.tandy

    Michael
     
  6. mario

    mario Guest

    I think you are talking about the Model 16 and 6000.
    I would really like it if I could find a place that documents the bus into
    which these cards plugged in, as well as the cards.
    I will. I hope it's still "alive".

    Thank you, Michael, for confirming the IC model.
     
  7. Eric Smith

    Eric Smith Guest

    There's a high probability that it's a house-numbered MC68000.
    GN7 is an MC68000 mask code, although it's remotely possible that
    the same mask code could have been used for some other part.
     
  8. Tim Wescott

    Tim Wescott Guest

    That 88xxx makes me suspicious -- are you sure it isn't an 88000 part of
    some sort?
     
  9. I wondered too. I thought their first RISC, before they got together
    with Apple, was the 88000 series.

    Michael
     
  10. Tim Wescott

    Tim Wescott Guest

    Yes it was. I've been told it's a nice processor, but rather a flop on
    the market -- they came out after ARM and MIPS. The Apple/Motorola/IBM
    (and HP IIRC) team was necessary to crash the market.
     
  11. Eric Smith

    Eric Smith Guest

    Yes, I'm sure. Those have too many I/O signals for a 64-pin DIP package.
     
  12. Eric Smith

    Eric Smith Guest

    I forgot to mention that SCxxxxx numbers (such as SC88019 on this part)
    are what Motorola (now Freescale) uses for house-numbered or custom
    parts, and the number generally has NO relation to a normal MCxxxxx
    number. Whereas XCxxxxx numbers are used on pre-qualification parts and
    are normally the same as the eventual MCxxxxx part number, other than
    the prefix.

    Since the part in question has the GN7 mask code, it's probably either
    just a house-numbered standard MC68000, or an MC68000 that has been
    tested to slighly different specifications than a standard one.
    Motorola did make some special MC68000-based parts with custom microcode
    for IBM for the XT/370 and AT/370 products, but those had unique mask
    codes.

    At one time, the data sheets on the MC68000 actually listed some minor
    differences between mask codes. For instance, on early mask codes, if a
    word write was performed to an odd address, both data strobes were
    asserted for the access even though it was automatically aborted and
    resulted in an Address Error exception. This resulted in memory
    corruption, which wasn't usually important because an Address Error was
    normally an unrecoverable error anyhow. But they fixed this on later
    mask codes so that the data strobes are not asserted in those
    circumstances.
     
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