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Re: [midatlanticretro] VAX 780 vs. 750

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  • Dave McGuire
    ... The 11/730 s implementation of the VAX instruction set is more heavily based in microcode than that of the 11/750, making it much smaller and much slower.
    Message 1 of 14 , Jul 1, 2013
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      On 07/01/2013 02:41 PM, David Riley wrote:
      > The 11/750 was a smaller, slower, cost-reduced version of the 11/780. The
      > 11/730 (even later), was a smaller, even slower, further cost-reduced version
      > of the same. My recollection is that most of the size and cost reduction was
      > accomplished by using more highly integrated gate arrays to replace discrete
      > TTL logic chips (which, at the time, were faster than the gate arrays).
      >
      > I believe the 11/730 was small enough to be easily rack-mountable, while the
      > 11/750 occupies most of a short cabinet. I could be misremembering, though;
      > I've never actually seen any in the flesh (part of why I'm excited for the
      > workshop).

      The 11/730's implementation of the VAX instruction set is more
      heavily based in microcode than that of the 11/750, making it much
      smaller and much slower. Basically fewer and fewer functions
      implemented in hardware, more and more functions implemented in microcode.

      The 11/730 CPU is built from Am2901 bit-slice chips. The control
      store (where microcode lives) is actually RAM, so when the 11/730 is
      powered up, it doesn't speak the VAX instruction set. Microcode is
      loaded from a TU58 tape cartridge into the control store by an
      8085-based service processor within the machine.

      Most 11/730 CPUs are in BA11-K style chassis, VERY compact by VAX
      standards of the day. Standard 19" rackmount.

      The VAX-11/725 is an 11/730 repackaged into a roll-around deskside
      chassis. The VAX-11/751 is a repackaged 11/750 that can be mounted in a
      standard 19" rack. The 751 was targeted at embedded and OEM applications.

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
    • Evan Koblentz
      ... Then we have no way to run it ... yet. :( It s possible that InfoAge s big temporary generator could make 3-phase. I do not know. I ll have to ask
      Message 2 of 14 , Jul 1, 2013
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        >> FYI, Evan, you'll need 208V 3-phase for the 11/780

        Then we have no way to run it ... yet. :(

        It's possible that InfoAge's big temporary generator could make 3-phase. I do not know. I'll have to ask Fred/Steve and get oodles of permission.
      • Dave McGuire
        ... I would not attempt that. No matter how good a temporary generator is, they are still much riskier than permanently-wired utility power in terms of
        Message 3 of 14 , Jul 1, 2013
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          On 07/01/2013 03:14 PM, Evan Koblentz wrote:
          >>> FYI, Evan, you'll need 208V 3-phase for the 11/780
          >
          > Then we have no way to run it ... yet. :(
          >
          > It's possible that InfoAge's big temporary generator could make
          > 3-phase. I do not know. I'll have to ask Fred/Steve and get oodles of
          > permission.

          I would not attempt that. No matter how "good" a temporary generator
          is, they are still much riskier than permanently-wired "utility" power
          in terms of power quality, harmonic distortion, frequency stability,
          etc. I would not EVER risk a machine like an 11/780 on temporary power.
          Ever. I strongly advise against attempting it until your primary
          utility power is restored.

          -Dave

          --
          Dave McGuire, AK4HZ
          New Kensington, PA
        • David Comley
          If there s room for one more, I have been thinking about putting my 11/750 on my small trailer and bringing it down to the August workshop. Might be useful to
          Message 4 of 14 , Jul 1, 2013
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            If there's room for one more, I have been thinking about putting my 11/750 on my small trailer and bringing it down to the August workshop. Might be useful to have two machines side by side to work on - and mine's mostly functional at this point (at least it was earlier this year).

            I have cables and odds and ends set up to boot the TU58 diagnostic tape images off my laptop if we get to that point, plus an RDM board for diagnostics.

            -Dave (C).


            From: David Riley <fraveydank@...>
            To: midatlanticretro@yahoogroups.com
            Sent: Monday, July 1, 2013 2:54 PM
            Subject: Re: [midatlanticretro] VAX 780 vs. 750

            Either way, I really meant I've never seen one *operating* in
            the flesh, though I suppose that's not as material to how much
            rack space it takes up.

            - Dave



          • Cory Smelosky
            ... I m gonna need to get out to the August workshop if that s gonna happen! ... -- Cory Smelosky http://gewt.net Personal stuff http://gimme-sympathy.org
            Message 5 of 14 , Jul 1, 2013
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              On Mon, 1 Jul 2013, David Comley wrote:

              > If there's room for one more, I have been thinking about putting my 11/750 on my small trailer and bringing it down to the August workshop. Might be useful to have two machines side by side to work on - and mine's mostly functional at this point (at least it was earlier this year).
              >

              I'm gonna need to get out to the August workshop if that's gonna happen!

              >
              > I have cables and odds and ends set up to boot the TU58 diagnostic tape images off my laptop if we get to that point, plus an RDM board for diagnostics.
              >
              >
              > -Dave (C).
              >
              >
              >
              > ________________________________
              > From: David Riley <fraveydank@...>
              > To: midatlanticretro@yahoogroups.com
              > Sent: Monday, July 1, 2013 2:54 PM
              > Subject: Re: [midatlanticretro] VAX 780 vs. 750
              >
              >
              >
              > Either way, I really meant I've never seen one *operating* in
              > the flesh, though I suppose that's not as material to how much
              > rack space it takes up.
              >
              > - Dave
              >
              >
              >

              --
              Cory Smelosky
              http://gewt.net Personal stuff
              http://gimme-sympathy.org Projects
            • tedheadster
              I expect I can have an OS disk and controller pre-loaded and ready to go for any VAX-11/750 that show up. This is all thanks to the beauty of the SIMH VAX
              Message 6 of 14 , Jul 1, 2013
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                I expect I can have an OS disk and controller pre-loaded and ready to go for any VAX-11/750 that show up. This is all thanks to the beauty of the SIMH VAX simulator.

                I build it on the simulator (runs _really_ fast), and then I just dump the finished bits onto a physical disk when done. That's what I did for both my PDP-11 and MicroVAX recently.

                So don't sweat the software part, let's focus on getting the hardware working.

                - Matthew

              • David Comley
                ... Sounds like a good plan. I m sure there will be challenges aplenty. Does anyone know how the MARCH 11/750 is equipped in terms of disk storage ? UDA50 or
                Message 7 of 14 , Jul 1, 2013
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                  From: tedheadster <whiteheadm@...>
                  To: midatlanticretro@yahoogroups.com
                  Sent: Monday, July 1, 2013 3:29 PM
                  Subject: Re: [midatlanticretro] VAX 780 vs. 750

                   So don't sweat the software part, let's focus on getting the hardware working.
                  Sounds like a good plan. I'm sure there will be challenges aplenty.

                  Does anyone know how the MARCH 11/750 is equipped in terms of disk storage ? UDA50 or other ?

                  -Dave

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