Loading ...
Sorry, an error occurred while loading the content.

Re: [midatlanticretro] VAX 780 vs. 750

Expand Messages
  • Dave McGuire
    ... The 11/750 is a cost-reduced machine. Much slower, lower power requirements, much cheaper. The 11/780 was built nearly entirely with 7400-series TTL
    Message 1 of 14 , Jul 1, 2013
    • 0 Attachment
      On 07/01/2013 02:30 PM, Evan Koblentz wrote:
      > I know the /80 was first; how did the /50 differ?

      The 11/750 is a cost-reduced machine. Much slower, lower power
      requirements, much cheaper. The 11/780 was built nearly entirely with
      7400-series TTL logic, while the 11/750 made use of large custom gate
      array chips for reduced the size and cost, and increased reliability.

      They both use Unibus for I/O, but the also each have an "internal"
      bus which is proprietary and specific to the machine...not the same
      between the 780 and 750.

      The 750 prototypes were deemed "too fast" and there was concern that
      they'd eat into the sales of the flagship 780, so a wait state circuit
      was added which slowed it down a bit. It could be disabled with one
      wire cut on the backplane, which many sites not under DEC field service
      did. It gave a noticeable performance boost.

      You remember my "corporate cabinet"-based PDP-11/70. The VAX-11/780
      CPU cabinet is not the same chassis, but they are of similar external
      dimensions. The 11/750 is one extended-width short rack a tad smaller
      than a washing machine.

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
    • Brian Schenkenberger, VAXman-
      ... The 11/780 was the first VAX. It was built primarily with discrete TTL logic. The 11/750 was subsequent to the 11/780 and was built using Gate Arrays.
      Message 2 of 14 , Jul 1, 2013
      • 0 Attachment
        David Riley <fraveydank@...> writes:

        >--BqNHK9zXsP9xi-rTkNIg4ETyjTgaeSiFZoZGmiM
        >Content-Type: text/plain; charset=us-ascii
        >Content-Transfer-Encoding: 7bit
        >
        >On Jul 1, 2013, at 2:30 PM, "Evan Koblentz" <evan@...> wrote:
        >
        >> I know the /80 was first; how did the /50 differ?
        >
        >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 11/780 was the first VAX. It was built primarily with discrete TTL logic.
        The 11/750 was subsequent to the 11/780 and was built using Gate Arrays. Both
        the 11/780 and the 11/750 implemented the full architecture instruction set of
        304 instructions and all 13 (if I've recalled and counted correctly) address
        modes. The 11/750 was significantly smaller and less expensive. I'd take, if
        I had the power, an 11/780 over an 11/750 any day.

        FYI, Evan, you'll need 208V 3-phase for the 11/780 and, likely, many other of
        the older kit that's been amassed.

        http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/vax/780/EK-SI780-IN-002_insta_Jan82.pdf

        Has details on installation and site requirements for the 11/780.

        --
        VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG

        Well I speak to machines with the voice of humanity.
      • Brian Schenkenberger, VAXman-
        ... I don t think one should consider racking a VAX 11/750. ;) A VAX 11/750 cabinet was about the size of an apartment clothes washer! -- VAXman- A Bored
        Message 3 of 14 , Jul 1, 2013
        • 0 Attachment
          David Riley <fraveydank@...> writes:

          >On Jul 1, 2013, at 2:45 PM, Evan Koblentz wrote:
          >
          >> >> I've never actually seen any in the flesh
          >>=20
          >> Didn't I show you our storage area at the last workshop? Our 750 is in th=
          >ere.
          >
          >You did. I don't remember seeing the 11/750, but it's probably
          >because there was so much to take in that I couldn't remember
          >it all. It was pretty well organized by the time I got there,
          >though!
          >
          >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.

          I don't think one should consider "racking" a VAX 11/750. ;)

          A VAX 11/750 cabinet was about the size of an apartment clothes washer!

          --
          VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG

          Well I speak to machines with the voice of humanity.
        • 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 4 of 14 , Jul 1, 2013
          • 0 Attachment
            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 5 of 14 , Jul 1, 2013
            • 0 Attachment
              >> 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 6 of 14 , Jul 1, 2013
              • 0 Attachment
                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 7 of 14 , Jul 1, 2013
                • 0 Attachment
                  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 8 of 14 , Jul 1, 2013
                  • 0 Attachment
                    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 9 of 14 , Jul 1, 2013
                    • 0 Attachment
                      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 10 of 14 , Jul 1, 2013
                      • 0 Attachment


                        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

                      Your message has been successfully submitted and would be delivered to recipients shortly.