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VAX 780 vs. 750

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  • Evan Koblentz
    I know the /80 was first; how did the /50 differ?
    Message 1 of 14 , Jul 1, 2013
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      I know the /80 was first; how did the /50 differ?
    • David Riley
      ... 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
      Message 2 of 14 , Jul 1, 2013
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        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).


        - Dave
      • Evan Koblentz
        ... Didn t I show you our storage area at the last workshop? Our 750 is in there.
        Message 3 of 14 , Jul 1, 2013
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          >> I've never actually seen any in the flesh

          Didn't I show you our storage area at the last workshop? Our 750 is in there.
        • David Riley
          ... 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
          Message 4 of 14 , Jul 1, 2013
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            On Jul 1, 2013, at 2:45 PM, Evan Koblentz wrote:

            > >> I've never actually seen any in the flesh
            >
            > Didn't I show you our storage area at the last workshop? Our 750 is in there.

            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.


            - Dave
          • 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 5 of 14 , Jul 1, 2013
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              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 6 of 14 , Jul 1, 2013
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                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 7 of 14 , Jul 1, 2013
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                  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 8 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 9 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 10 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 11 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 12 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 13 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 14 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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