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  1. Consider too the use of Ruud's diagnostic ROM....

    Consider too the use of Ruud's diagnostic ROM. See [here].

    The kind of output expected from that for failed RAM bits is shown at [here].
  2. Expect a screen similar to that shown at [here...

    Expect a screen similar to that shown at [here]. That screen was produced when I simulated a failure of bit 2 in bank 0. Note the row in the bottom-right labeled "FAILING BITS" and how in that row,...
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    See the 'Setups' section of [here...

    See the 'Setups' section of [here].
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    When member MicroCoreLabs posted photos of his...

    When member MicroCoreLabs posted photos of his set, I noticed that his set (both the 5000026 and 5000027 chips) had markings/scratches that matched with Tyler's set. It was particularly noticeable...
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    Worth doing because you may then see a copper...

    Worth doing because you may then see a copper track (or more) that has been eaten through. If the case, there may be someone local who can repair the track for you.
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    Which suggests that the content is not...

    Which suggests that the content is not corrupt/damaged (i.e. not the cause of your non-working 5150).


    Like the 'NEC D2364' on one my early 5160 motherboards, pictured in the top photo at [here]....
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    :) So, how about "Uh-oh" if the BIOS ROM...

    :) So, how about "Uh-oh" if the BIOS ROM experiences a read/write error ?
    Or, the sound of a head crash if the BIOS ROM can no longer communicate with the IDE/CF device ?
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    If that IBM 5170 was recently acquired by you,...

    If that IBM 5170 was recently acquired by you, and, had not been powered on in years (or was only powered briefly), then based on my experience, I do not consider your experience (multiple tantalum...
  9. Educated guess: The SW1/SW2 settings may be...

    Educated guess:

    The SW1/SW2 settings may be per the IBM PC (IBM 5150), shown at [here].

    However, because the motherboard contains a serial port and parallel port, I would expect that a...
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    Cylinders = 306 / Heads = 8 / SPT = 17 / ...

    Cylinders = 306 / Heads = 8 / SPT = 17 / WPC = 128


    According to my notes, it was one of the 20MB drives that IBM optionally supplied in the later model 5160's (together with the third...
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    With the 'power' LED being on, I think you can...

    With the 'power' LED being on, I think you can safely assume that the power supply unit (Toshiba name it the "AC PS Unit") is functional. I could not see anything in the maintenance manual where one...
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    It will be an XT-class MFM controller going into...

    It will be an XT-class MFM controller going into your 5150.

    In case you are unaware, be aware of the information at [here]. Additional info at [here].


    The only way to guarantee (repeat:...
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    That's what I am putting my bet on.

    That's what I am putting my bet on.
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    It is possible that two distinct problems are...

    It is possible that two distinct problems are present, one relating to the hard drive, and one related to video. Maybe both are related to each other. But, I think that you should treat them as...
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    A POST code reader on the parallel port can...

    A POST code reader on the parallel port can sometimes help. On my functional 430CDT, powering it up with one of [these] connected to the parallel port, results in POST codes being displayed, per...
  16. Thread: IBM 5170 Issue

    by modem7
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    No, not via RAM. They are I/O reads and writes...

    No, not via RAM. They are I/O reads and writes between the CPU and DMA controller (with various chips between the two).

    IBM BIOS - POST (power-on self test)

    First, the POST is not a...
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    So, that rules out interference from a bit 6 chip...

    So, that rules out interference from a bit 6 chip in another bank.


    Still waiting for the 74LS245 to arrive?

    Do you have a logic probe ?

    Have you used a multimeter to verify trace...
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    Does the 16K CRITICAL MEMORY REGION test pass if...

    Does the 16K CRITICAL MEMORY REGION test pass if the RAM chips are removed from the other banks (1/2/3) ?
  19. Thread: IBM 5170 Issue

    by modem7
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    Welcome to these forums. I do not know what...

    Welcome to these forums.


    I do not know what you mean by "direct write". I/O type writes and writes are being done. Looking at the source code, I agree with your "basically writing FF, 55 and AAh...
  20. Toshiba T1950CT maintenance manual at [here...

    Toshiba T1950CT maintenance manual at [here].
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    Yes. Either on its own, or in addition to the...

    Yes. Either on its own, or in addition to the AT-class MFM controller. If on its own, you would normally set the hard drive number in 'CMOS SETUP' to zero, otherwise the motherboard's POST will...
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    DOS BIOS Hardware I.e. DOS...

    DOS <--> BIOS <--> Hardware
    I.e. DOS communicates with a hard disk BIOS (wherever that BIOS is located) and that BIOS communicates with the controller and hard disk (the hardware).

    As for the...
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    The code is 8 KB sized, and so at minimum, you...

    The code is 8 KB sized, and so at minimum, you will need a 2764 (with adapter). But you can use a 27128 (with adapter) if you double up the 8 KB code in the 27128. Or use a 27256 (with adapter) if...
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    There were a few contributors. A 'thank you' to...

    There were a few contributors. A 'thank you' to Rudd for his diagnostic, an additional tool to assist in regard to RAM issues, particularly given that the RAM component of the Supersoft/Landmark...
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    And you have the satisfaction of fixing another...

    And you have the satisfaction of fixing another motherboard.

    Having a quick look back through the posts, the root cause is multiple bad RAM chips in bank 0. Do you agree? I will add the...
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