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Re: Newbie

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  • Larry T.
    ... Jerome In my experience, the most likely causes of this kind of behavior are: 1) a bad memory chip 2) a bad buffer chip The only way to tell for sure is to
    Message 1 of 6 , Mar 1, 2004
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      --- In altaircomputerclub@yahoogroups.com, "caljer" <caljer@y...>
      wrote:
      > Thx Steve. Exactly, window dressing!
      > I try to run the small addition program from the manual, but as I
      > said in my first post, whatever I deposit in a memory location has
      > bit D4 ON. (i.e. if I Deposit 00 000 000, I get 00 010 000 when I
      > Examine) So I have to check the wiring. I already cleaned the edge
      > connectors. The wiring is a little more involved...
      > Any other idea for this kind of behavior?

      Jerome

      In my experience, the most likely causes of this kind of behavior are:
      1) a bad memory chip
      2) a bad buffer chip
      The only way to tell for sure is to know the layout of the memory
      board. If there is more then one bank of ram chips and you know the
      size of the chips, pick an address that would be in a different bank
      of ram chips and see if the same bit is still 'stuck' after you
      deposit data. If there are more then two banks of chips, try this
      with each seperate bank. If it is a bad ram, only bad banks will
      show the problem, and if more then one bank is bad, the may well have
      the problem with a different bit. Be sure to test will all 0's AND
      all 1's! You might have problems such that you will always get a 0 no
      matter what data you poke! If you have mulitple memory boards, be
      sure to try all of the boards. If is is a buffer chip, all memory on
      the same board will have the problem. If all boards have the problem,
      then it is likely a buffer on the cpu board (I don't remember the
      Altair from panel having buffers for the data lines, but if so the
      problem may be there).

      Larry
    • Erik Klein
      Which store in Mountain View was it? I work off of Castro and would be curious if I d ever passed it and missed the old box. I ve seen similar memory issues
      Message 2 of 6 , Mar 1, 2004
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        Which store in Mountain View was it? I work off of Castro and would be curious if I'd ever passed it and missed the old box.

        I've seen similar memory issues on my machines before. One possible issue could be a simple short in the bus. If one of the memory lines is shorted to another tied high or low then you might see a "stuck bit' situation.

        BTW, only some of the messages in this thread are making it to my inbox for some reason. I never did see your original post. . .

        Erik Klein
        www.vintage-computer.com
        www.vintage-computer.com/vcforum
        The Vintage Computer Forum


        caljer <caljer@...> wrote:
        Thx Steve. Exactly, window dressing!
        I try to run the small addition program from the manual, but as I
        said in my first post, whatever I deposit in a memory location has
        bit D4 ON. (i.e. if I Deposit 00 000 000, I get 00 010 000 when I
        Examine) So I have to check the wiring. I already cleaned the edge
        connectors. The wiring is a little more involved...
        Any other idea for this kind of behavior?

        I posted a higher def pic of the wire wrap board. The board has an
        UART TMS 6011 and two 555. I believe that it was wired as a dual
        function tape recorder interface and serial interface. But it's a
        guess based on connectors as well as schematics in the binder.


        Jerome


        --- In altaircomputerclub@yahoogroups.com, "Steve" <alltare@y...>
        wrote:
        > Thanks for posting the pictures. Your computer looks pretty
        clean.
        > Was the music store using it for anything other than a blinky-light
        > window dressing? Have you been able to run any programs on it
        yet?
        > What's the function of the blue wire wrap board in the pictures
        > labeled "MyAltair8800_10" and "MyAltair8800_11"?
        >
        > Steve
        > ==========================
        >
        > --- In altaircomputerclub@yahoogroups.com, "caljer" <caljer@y...>
        > wrote:
        > > Hello,
        > >
        > > I'm the proud owner of a MITS Altair 8800 serial# 222027K
        acquired
        > > sometime in 2003. I got it from a music store in Mountain View,
        CA.
        > > The computer was on display in the store window among various
        music
        > > intruments and with its LEDs blinking. I had to look several
        times
        > to
        > > make sure it was not some kind of fake computer. Kind of a chock,
        > > being a member of the Computer History Museum in Mountain View.
        > > <http://www.computerhistory.com>. I can now brag about it ;-)
        > >
        > > Anyway I have it now and it was sitting in my garage until today.
        I
        > > tested it (looks like one bit is stuck in ON when I deposit and
        > > examine a memory position). It's kind of fun to read the manual
        and
        > > play with this toy. Reminds me my early computer day with the PET
        > > Commodore and the Apple II. Documentation was included with lots
        of
        > > notes and schematics.
        > > I shot some pictures and posted them in the Photos section here.
        > >
        > > Enjoy and let me know waht you think of this baby,
        > >
        > > Jerome



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      • Steve
        Jerome, Your guess about it being a tape interface makes sense to me. One of the quirks of Yahoo is that only the person who posted a photo and the group
        Message 3 of 6 , Mar 1, 2004
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          Jerome,

          Your guess about it being a tape interface makes sense to me.

          One of the quirks of Yahoo is that only the person who posted a photo
          and the group moderator are able to see the full size image.
          Everyone else has to live with a so-called "screen size" image that's
          usually only about 400 pixels wide. You can get around this by
          posting your image in the FILES folder rather than the PHOTOS
          folder. I've created a folder in FILES called JEROME, and I've put
          the full size image there.

          Besides doing the checks that Larry discussed, take the time to read
          through the message archives about other memory problems. You might
          find something useful. Also, check the white wires that run from the
          first mother board to the front panel. It's common to have one or
          more of them break off where they're soldered. Your computer was
          built a little differently than most. Usually, the first mother
          board was installed fully to the right side (as viewed from the
          front) of the computer. The 2nd, 3rd, and 4th mothers would then be
          added to the left of the 1st one. Your builder started in the
          middle. There's nothing wrong with that, but it does leave the white
          wires a little more vulnerable and messy than would otherwise be the
          case. Look at pictures of other 8800s and you'll see what I mean.

          You probably already know this, but let me give this warning anyway.
          When you're troubleshooting, NEVER pull a board out of the buss with
          the computer powered up. You'll most likely cause catastrophic
          damage. This has been discussed in the archives too.

          Steve
          ========================

          --- In altaircomputerclub@yahoogroups.com, "caljer" <caljer@y...>
          wrote:
          > Thx Steve. Exactly, window dressing!
          > I try to run the small addition program from the manual, but as I
          > said in my first post, whatever I deposit in a memory location has
          > bit D4 ON. (i.e. if I Deposit 00 000 000, I get 00 010 000 when I
          > Examine) So I have to check the wiring. I already cleaned the edge
          > connectors. The wiring is a little more involved...
          > Any other idea for this kind of behavior?
          >
          > I posted a higher def pic of the wire wrap board. The board has an
          > UART TMS 6011 and two 555. I believe that it was wired as a dual
          > function tape recorder interface and serial interface. But it's a
          > guess based on connectors as well as schematics in the binder.
          >
          >
          > Jerome
          >
          >
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