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Thread: IBM 5170 post code 201

  1. #1

    Unhappy IBM 5170 post code 201

    Hi !
    I'm having some difficulties repairing my 5170 (type 3), let me explain :

    At boot, it is always displaying the code 000000 FFFF 201 and hangs there.
    If I boot it with supersoft diag roms, everything looks okay (with the same quirks as described on minuszerodegrees.com)
    IMG_20180809_200503.jpg

    I've tried flashing fresh EPROMs with the latest IBM BIOS : same!
    I've also tried resetting the CMOS to no avail...

    So I really don't know what to do at this point, can someone help me ?
    Thanks

  2. #2
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    On MZD's 5170 error code list, the following note is given under error 201:

    Displayed on screen in the format of "AAAAAA BBBB 201-Memory Error",
    where AAAAAA is the hexidecimal address (in bytes) of the failing word and BBBB shows which bits in the word have failed

    NOTE: If the BBBB portion (failing bits) contains many "F", example: "FFFE", then it is highly likely that non-existing RAM is being tested.
    For example (one of many), this would occur if the machine SETUP is configured for 640K of RAM, but only 512K is fitted.
    For example (one of many), a RAM card has failed completely.

  3. #3

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    Yes, I do know the error code 201 explanation, but as you can see my RAM is tested good by supersoft diag and my error code indicates the first byte of RAM is in error so it can't be a memory size detection problem...
    I have no RAM card installed and if the first 16k bytes of ram were bad, the motherboard would appear dead...

  4. #4
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    Similar error found in this forum thread :

    http://www.vcfed.org/forum/showthrea...00000-FFFE-201

  5. #5
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    Very interesting that the IBM BIOS ROMs have issue testing RAM, but the Supersoft diagnostic ROMs do not.

    One difference that I expect between the two is timing; I expect that the Supersoft diagnostic does its RAM tests later.

    What power supply are you using? I have seen problems caused by XT-class power supplies, and there may be some clone AT-class power supplies that are a problem (e.g. faked POWER GOOD signal not delayed enough). Just a 'shot in the dark'.

  6. #6

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    I'm using my test power supply which is from a way more recent 486 DX2 50Mhz system, I'm not using the original 5170 power supply because I don't want to switch it on and off repeatedly for testing purpose (I didn't recap it, for now it is 100% stock)

    I will try with the original 5170 supply, I will also try connecting the PG signal a few seconds after power on.
    I wanted to try another BIOS (a third party one), but I'm out of EPROM and I don't have a UV lamp...

  7. #7

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    OK, so I've tried with the original 5170 power supply : same result, also tried connecting the PG signal 10 seconds after power-on, same

    It must be something in the IBM BIOS code that isn't strictly tested by the Supersoft diagnostic ROMs... (Timing related ?)

    I've ordered a dozen 27C256 to try third party BIOSes, maybe they will work or give me a different error code...

  8. #8

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    So... I've flashed two 27C256 with the AMI Bios from MZD.com and it doesn't boot, it gives me 3 beeps which mean for AMI BIOSes : Base 64K RAM Error
    Different BIOSes, same memory error!
    To be sure of Supersoft diagnostic, I let it run for a few hours : no memory errors then I tried to remove a RAM chip : error detected with correct bit identification.
    So the Supersoft diag ROMs are working as expected and my RAM should be good.
    Now, I really don't know what to try next

  9. #9
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    Quote Originally Posted by Alois54 View Post
    Now, I really don't know what to try next
    It's odd.

    If this were my motherboard, I would probably ignore the Supersoft diagnostic results, refit the IBM BIOS ROM's, then attack the symptom using a logic state analyser.

  10. #10

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    Quote Originally Posted by modem7 View Post
    If this were my motherboard, I would probably ignore the Supersoft diagnostic results, refit the IBM BIOS ROM's, then attack the symptom using a logic state analyser.
    Yup, already launched PulseView
    I'm going to check the clock circuit first because I have a 5162 which had the same problem before dying completely (I bought them together also with a 5150 and a 5160, I've only repaired the 5160 so far by changing 2 RAM chips and 3 caps)
    and on the 5162 the clock signal is now completely nuts (I've ordered a 82284 and I'm going to check the 2 caps on the crystal)

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