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Re: Notes on MSI/88e Deconstruction.

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  • Mark Graybill
    As to sockets, for breadboarding one of the cheesy sockets with the thin flat bendy legs is good enough, that and hoping the chip won t pop out at an odd
    Message 1 of 2 , Jun 5, 2003
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      As to sockets, for breadboarding one of the cheesy sockets with the thin
      flat bendy legs is good enough, that and hoping the chip won't pop out at an
      odd moment (or the wires or other bits.) For construction, yeah, there's
      nothing like a good machined pin socket, and hopefully I'll find a board
      that has a 40-pin one in it that I can scrap one out of, since I don't want
      to use my last two 28-pin machined pin sockets for the job. I'm pretty cheap
      when it comes to chips, and even cheaper when it comes to sockets, I'm
      afraid.

      As to tracing out the circuit on the MSI/88e, yeah, it looks pretty
      standard, except for the quick fix on the clock circuit and wanting to know
      the details on where all the traces go. I went through some of the old posts
      and I agree about needing to have bare boards to do a good job of tracing
      everything. I'm working half on pulled parts and half on conjecture where
      the parts haven't been pulled yet.

      The one I'm tearing down, and at least two others I've opened up, have a
      quick fix to the clock circuit. It looks like that circuit was originally on
      the CPU board, since there are places on the board for the components, and
      got moved to the display board afterward. I'm guessing they ran into
      mechanical interference at the very least, particularly with the crystal.

      Lee, I don't suppose that part of the circuit you've got documented is the
      chip select/enable logic for the ROM? It's possible that I fried the chip
      during removal or with handling, but I've got a pretty good record on that
      count in the past, so I'm guessing the chip isn't a straight 2764 and I need
      to do something like invert the chip enable.

      TIA,

      Mark G.
    • Lee Hart
      ... No, it s not a 2764 pinout but it s close. ROMs have extra pins, since you don t need to program them. They used the extra pins for additional chip
      Message 2 of 2 , Jun 6, 2003
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        Mark Graybill wrote:
        > Lee, I don't suppose that part of the circuit you've got documented
        > is the chip select/enable logic for the ROM? ... I'm guessing the
        > chip isn't a straight 2764 and I need to do something like invert
        > the chip enable.

        No, it's not a 2764 pinout but it's close. ROMs have extra pins, since
        you don't need to program them. They used the extra pins for additional
        chip selects. I'll get my notes and type up what I've found, and get
        back to you.
        --
        Lee A. Hart Ring the bells that still can ring
        814 8th Ave. N. Forget your perfect offering
        Sartell, MN 56377 USA There is a crack in everything
        leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
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