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Thread: 5150 Supersoft Memory faulire - Which Chip ?

  1. #11
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    Quote Originally Posted by KLund1 View Post
    05040 then 04000
    Same as what I see, so we ignore that.

    Quote Originally Posted by KLund1 View Post
    Also with the same failing bits.
    But what are those bits ? All I have to refer to is the photo in post #1 where the display is corrupted with things doubled up.

  2. #12
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    See pic in post #6
    bits 7 to 1 are X'd
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  3. #13
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    Quote Originally Posted by KLund1 View Post
    See pic in post #6
    bits 7 to 1 are X'd
    From my perspective, that was when you populated banks 1/2/3, thus possibly introducing extra faulty bits (due to bad chips).
    But I will take it from your answer, that with the RAM in banks banks 1/2/3 removed, the diagnostics show faulty bits of 7 to 1.

    That is a lot of bits, and interesting that bit 0 always shows as good.

    Originally, I used to think that the 16K CRITICAL MEMORY REGION test did not rely on operational RAM refreshing (that the later RAM test did), but by experiment, I discovered that it did. At post #39 at [here] are some results of mine from simulating failure of RAM refresh, and seeing what the impact was on the 16K CRITICAL MEMORY REGION test. Then, I saw only one or two bits reported in error, and they varied.

    However, maybe the count of bits depends on the particular motherboard.

  4. #14
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    Also very interesting. But is starting to sound more like the ram system, and not only the ram chips.
    But I am still willing pull 1 or more ram chips off the board. I'd like to have some idea of which one(s) to pull and see what happens with other ram chips
    What do you think?
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  5. #15
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    Quote Originally Posted by KLund1 View Post
    Also very interesting. But is starting to sound more like the ram system, and not only the ram chips.
    But I am still willing pull 1 or more ram chips off the board. I'd like to have some idea of which one(s) to pull and see what happens with other ram chips
    What do you think?
    I guess try replacing any one between 7 and 1. If that bit disappears from the diagnostic's list, you then assume that the other six RAM chips are bad as well. If not, more diagnosis required.

  6. #16
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    I do not know if you have had a chance yet to replace one of the indicated failing bits, but something interesting turned up.

    Quote Originally Posted by modem7 View Post
    That is a lot of bits, and interesting that bit 0 always shows as good.
    A recent post about the Supersoft ROM running on an IBM 5170 that has no RAM at all fitted, showed similar: bit 0 passing, and bits 1 though 7 failing.
    Photo at [here].

    On my IBM 5160, I repeated the no-RAM exercise (using the 5150/5160 version of the Supersoft ROM), and got the same result: bit 0 passing, and bits 1 though 7 failing.
    Photo at [here].

    Quote Originally Posted by KLund1 View Post
    But is starting to sound more like the ram system, and not only the ram chips.
    Yes it does look that way.

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