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Thread: Project: Micro 8088 - Chipset-based 8088 XT compatible processor board

  1. #91
    Join Date
    Dec 2018
    Location
    St. Petersburg, Russia
    Posts
    6

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    Quote Originally Posted by nztdm View Post
    Have you tried another power supply?
    Try reseating FE2010A. Do you have a PLCC extractor tool to do this safely?
    I did have an issue like this until I replaced an FE2010A. I've also had an FE2010A with bad DMA controller.
    No effect running at 4.77MHz instead of 9.55MHz?
    Will definitely work at 4.77MHz with 74LS, and possibly at 9.55. So those are likely not the issue.
    Are the edge fingers very worn on your card?
    Tried other ISA slots?
    Yes, I've tried 2 different PSUs and reseating FE2010A - same results. Changing ISA slots (for both CPU & VGA) made some VGA cards produce different errors (IO NMI for OTI-037, RAM errors for Tseng), when I was getting image out of them.
    I was able to switch to 9.55 only with FDC card, everything else was at 4.77 MHz. Edge connector has some damage since it's HASL, not gold-plated, but it doesn't look that bad.

  2. #92

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    Quote Originally Posted by Jager
    Things i've tried so far:
    1) Swapped around memory & logic ICs, tried different CPU, just in case - no effect.
    2) Replaced F-series ICs (some of them were used) with new LS/ALS chips - no effect.
    3) Checked the pull-up resistors (Resistance looks OK, got +5V on data lines with LS245 removed) & tried adding ones to the backplane - no effect.
    Hope it's not FE2010A, since it's kinda expensive.
    Quote Originally Posted by nztdm View Post
    Are the edge fingers very worn on your card?
    If they are HASL finished instead of ENIG + Gold Fingers and I had to bet, I would bet that is the reason.

    In that case, try cleaning them with isopropyl alcohol.

  3. #93
    Join Date
    Dec 2018
    Location
    St. Petersburg, Russia
    Posts
    6

    Default

    Quote Originally Posted by spark2k06 View Post
    If they are HASL finished instead of ENIG + Gold Fingers and I had to bet, I would bet that is the reason.

    In that case, try cleaning them with isopropyl alcohol.
    Nope, cleaning didn't help.
    And the data bus is actually OK - turned out CE on LS245 was mostly high at these moments and only "0" were transmitted, so that's normal.
    I've also tried another video card - AVGA2. It works perfectly until either F1 is pressed for bios settings or XT-IDE bios loads up. After that the whole screen becomes a colored mess.

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