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Resetting the Altair

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  • Steve
    From MITS Computer Notes periodical, Vol1 #5 P19. They didn t know why, even when they were making them! Steve
    Message 1 of 5 , Aug 13, 2009
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      From MITS 'Computer Notes' periodical, Vol1 #5 P19.  They
      didn't know why, even when they were making them!



      Steve

    • tdurston
      Hi Steve, That s odd... but so were a lot of things in those days. The we in the article could be the writers of MITs Computer Notes winging it , or maybe
      Message 2 of 5 , Aug 13, 2009
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        Hi Steve,

        That's odd... but so were a lot of things in those days.

        The "we" in the article could be the writers of MITs Computer Notes "winging it", or maybe they asked the CPU / front panel design engineer, Bill Yates (who sometimes gave unintelligible answers), or?

        I recall technical concepts of reliable Power-On-Reset (POR) circuits were not fully understood or implemented at the time the original Altair was designed. Thus the hard RESET recommendation to assure a known good reset condition of all registers on all boards.

        Note that even IBM PCs, PC-ATs and clones had a RESET button that occasionally needed whacking. Even these days I see circuits designed that do not provide a reliable reset on power-up or during brownout/power surges.

        Tom Durston

        --- In altaircomputerclub@yahoogroups.com, "Steve" <alltare@...> wrote:
        >
        >
        > From MITS 'Computer Notes' periodical, Vol1 #5 P19. They
        > didn't know why, even when they were making them!
        >
        >
        >
        > Steve
        >
      • Steve
        It s from a list of operation and construction tips submitted by an LA dealer, the Arrowhead Computer Company/The Computer Store. I think the stop/reset switch
        Message 3 of 5 , Aug 13, 2009
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          It's from a list of operation and construction tips submitted by an LA dealer, the Arrowhead Computer Company/The Computer Store.

          I think the stop/reset switch combo had something to do with inhibiting the action of most of the front panel's one-shots, but since I've never been curious enough to investigate it, that's just a guess.

          I remember reading (30 years ago)that the 8800b's new front panel, without one-shots, was supposed to have fixed whatever bug that had necessitated the 2-fingered reset. However, I've had to use it often on those models too.

          It's interesting that the switch sequence had already become a poorly understood "tradition" after just a few months of Altair production. I look at it as early training for Windows' "3-finger salute" (CTRL-ALT-DEL).

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

          --- In altaircomputerclub@yahoogroups.com, "tdurston" <tdurston@...> wrote:
          >
          > Hi Steve,
          >
          > That's odd... but so were a lot of things in those days.
          >
          > The "we" in the article could be the writers of MITs Computer Notes "winging it", or maybe they asked the CPU / front panel design engineer, Bill Yates (who sometimes gave unintelligible answers), or?
          >
          > I recall technical concepts of reliable Power-On-Reset (POR) circuits were not fully understood or implemented at the time the original Altair was designed. Thus the hard RESET recommendation to assure a known good reset condition of all registers on all boards.
          >
          > Note that even IBM PCs, PC-ATs and clones had a RESET button that occasionally needed whacking. Even these days I see circuits designed that do not provide a reliable reset on power-up or during brownout/power surges.
          >
          > Tom Durston
          >
          > --- In altaircomputerclub@yahoogroups.com, "Steve" <alltare@> wrote:
          > >
          > >
          > > From MITS 'Computer Notes' periodical, Vol1 #5 P19. They
          > > didn't know why, even when they were making them!
          > >
          > >
          > >
          > > Steve
          > >
          >
        • toml_12953
          ... Many clones did but the real IBM PC, XT and AT did not. I have them here and I can t see any sign of a reset switch!
          Message 4 of 5 , Sep 2, 2009
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            --- In altaircomputerclub@yahoogroups.com, "tdurston" <tdurston@...> wrote:
            > Note that even IBM PCs, PC-ATs and clones had a RESET button that occasionally needed whacking. Even these days I see circuits designed that do not provide a reliable reset on power-up or during brownout/power surges.
            >
            > Tom Durston

            Many clones did but the real IBM PC, XT and AT did not. I have them here and I can't see any sign of a reset switch!
          • tdurston
            ... Woops. My fuzzy memory seems to recall the IBM PC 5150 I bought 2nd hand did have a small red reset button on the back of the PC. I d guess the hacker I
            Message 5 of 5 , Sep 2, 2009
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              --- In altaircomputerclub@yahoogroups.com, "toml_12953" <tlake@...> wrote:
              >
              > --- In altaircomputerclub@yahoogroups.com, "tdurston" <tdurston@> wrote:
              > > Note that even IBM PCs, PC-ATs and clones had a RESET button that occasionally needed whacking. Even these days I see circuits designed that do not provide a reliable reset on power-up or during brownout/power surges.
              > >
              > > Tom Durston
              >
              > Many clones did but the real IBM PC, XT and AT did not. I have them here and I can't see any sign of a reset switch!
              >
              Woops. My fuzzy memory seems to recall the IBM PC 5150 I bought 2nd hand did have a small red reset button on the back of the PC. I'd guess the hacker I purchased it from added some wires to pins 20 and 21 of the 8088 (By Bridging Pins 20 and 21 of the 8088 CPU, you can hard reset the system).

              But you are correct, I believe only clones had reset buttons (very handy, too). Thanks for clearing my misconception. TomD
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