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1225Re: [midatlanticretro] Which version is it, Altair 680 or 680b ?

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  • billdeg@aol.com
    Sep 5, 2005
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      I should say that I could be totally wrong...I don't have a 680, but I have
      seen in a couple here and there. I actually read about the B when reading up
      on my SWTPc 6800. I can't remember exactly where. Definately the IC L was
      made with a blank on the "B" unless you added the optional serial ROM for the
      slot. I don't know if the non-B 680 would have the slot or not, but I would
      focus on that part of the card, try to find a schematic that compares the two to
      get your answer about the rev of your particulat 680.

      Bill D

      In a message dated 9/5/2005 8:56:32 AM Eastern Standard Time,
      ragooman@... writes:

      > I couldn't tell which month in '76 this mainboard might have been made.
      > Is yours a 608b too then ? I was hoping the Rev # would give a clue. The
      > mainboard does have a place for IC L (74LS74), but the socket is empty.
      > So would the 680 version have a blank spot there w/o any traces ? I
      > recall seeing pictures online of the early 680's with a beige front
      > panel, mine isn't. I guess then this might be a 680b after all.
      > I think my brother never ordered this with the Monitor Rom, because that
      > socket is empty. The System Monitor manual still has the source code in
      > there. The title in there mentions 680b Prom Monitor. I'll have to try
      > and dig up some 1702 Roms and program some, I hope I get a good one.
      > This might be a good time to build a rom emulator.
      > I think I remember why now we had to build an ascii keyboard w/ parallel
      > intfc for this. We didn't have a terminal back then to use if we had a
      > Monitor Rom. So we had this wired up to the machine as an I/O port
      > instead. Looking through some of the code listings on an old notepad, I
      > found a code listing for a Monitor code which allowed us to read from
      > the ascii keyboard. Basically, this code was modified from the original
      > Monitor Rom and skipped over the ACIA serial chip instead and read from
      > a memory-mapped I/O port.
      > =Dan
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