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Looking for the dimensions or form factor of the baby AT board

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    #31
    Wasn't the IBM 5162 (XT-286) the prototypical baby AT motherboard? That's my memory of it.

    - Alex

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      #32
      As promised, here are my findings of the dimensions of various boards I have and the coordinates of the most important parts, What do I consider as an important part:
      - the holes
      - the ISA slots
      - the keyboard and cassette connector.
      IMHO the 12-pins connector is not an important part: you can place it almost anywhere on the board and the board will still be functional inside a case. But move the keyboard connector a centimeter to the right or the left and I don't think you can plug a keyboard into it anymore.

      I will give you the images of the boards as I have saved them in Eagle (packages, to be precise) and I will give you the coordinates of the various parts in inches.

      But what to use as base coordinate? To make a long story short, I used the upper-left pin of ISA slot 1 as base.


      I start with my 5160 clone board base.

      The board:
      - left edge of the board: -0.12
      - top edge of the board: 1.0
      - bottom edge of the board: 11.0
      - right edge of the board: 8.38

      The holes:
      - top-left: 0.58 - 0.6
      - top-middle: 3.58 - 0.6
      - top-right: 8.18 - 0.6

      - middle-left: 0.58 - -5.0
      - middle-middle: 3.58 - -5.0
      - middle-right: 8.18 - -5.0

      - bottom-left: 0.58 - -10.8
      - bottom-middle: 3.58 - -10.8
      - bottom-right: 8.18 - -10.8

      Keyboard connector: the middle between the two drill holes: 7.25 - 0.7

      Distance between upper-left pins of ISA slots: 0.8


      The IBM 5160 board is the same with one exception: the middle-right hole is missing.


      The 5150 board is the same as the 5160 clone board except:
      Keyboard connector: 6.85 - 0.7
      Cassette connector: 5.95 - 0.7
      Distance between upper-left pins of ISA slots: 1.0


      The AT clone board is the same as the 5160 clone board except:
      It is wider, left edge of the board: -0.17
      Keyboard connector: the middle between the two drill holes: 7.45 - 0.7

      The library with the packages is free.
      With kind regards / met vriendelijke groet, Ruud Baltissen

      www.baltissen.org

      Comment


        #33
        Back in the day I bought a 286-12 board that dropped nicely into a clone XT case. The only problem was that I managed to pull the timing crystal out of the motherboard first time around. It hung up on the left drive cage. I put the crystal back in backwards, but the dealer was kind enough to point out my error. The second time around it went in easy peasy once I knew what to watch out for.

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          #34
          Crystals have polarity? Maybe you meant XCO (crystal controlled oscillator)?
          Reach me: vcfblackhole _at_ protonmail dot com.

          Comment


            #35
            Originally posted by Chuck(G) View Post
            Crystals have polarity? Maybe you meant XCO (crystal controlled oscillator)?
            Could be. It was back in the 1980s. Sue me.
            All I remember is was silver, rectangular, and had a relatively thick wire lead coming from each corner. I hooked it with the left-hand drive cage while installing the motherboard & pulled it out. I put it back in and nothing happened, so I took it back to the store where I got it. (remember when there were local brick & mortar computer parts stores?) The owner informed me I had put it in wrong fixed it. Got a dirty look too.

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