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Re: [midatlanticretro] Re: Tape Drives

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  • Dave McGuire
    ... Most machines that require an M-G did because they required 400Hz power, and an M-G is the most efficient way to get it. But yes, your point is well
    Message 1 of 23 , Aug 7, 2013
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      On 08/07/2013 11:09 PM, Jeff Jonas wrote:
      >>> Be aware that TU77/TU78 drives can pull surges of 400A.
      >>> No typo there.
      >
      > Wowzers! That needs a REAL "monster cable" :)
      > No wonder the big iron required a motor-generator.
      > That gives REAL isolation!

      Most machines that require an M-G did because they required 400Hz
      power, and an M-G is the most efficient way to get it. But yes, your
      point is well taken. :)

      -Dave

      --
      Dave McGuire, AK4HZ
      New Kensington, PA
    • Dave McGuire
      ... A lot of non-Navy gear requires 400Hz power. Most large Crays and CDC machines come to mind. Smaller inductors and capacitors in the power supplies.
      Message 2 of 23 , Aug 7, 2013
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        On 08/07/2013 11:23 PM, David Riley wrote:
        > On Aug 7, 2013, at 11:09 PM, "Jeff Jonas" <jeff_s_jonas@...> wrote:
        >
        >>>> Be aware that TU77/TU78 drives can pull surges of 400A.
        >>>> No typo there.
        >>
        >> Wowzers! That needs a REAL "monster cable" :)
        >> No wonder the big iron required a motor-generator.
        >> That gives REAL isolation!
        >>
        >> By the way, MARCH has a M-G set that's
        >> 400 Hz, 120 V, about 1 kVA.
        >> I'm unsure that's enough to power even ONE Univac.
        >
        > Also, what do we have that runs on 400 Hz? We don't have much naval equipment that I know of.

        A lot of non-Navy gear requires 400Hz power. Most large Crays and
        CDC machines come to mind. Smaller inductors and capacitors in the
        power supplies.

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
      • Jeff Jonas
        ... Another factor is blocksize, which may contain several records that are deblocked/gathered beforehand by software. Backups use LARGE block sizes to keep
        Message 3 of 23 , Aug 7, 2013
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          > Keep in mind, tapes in that era were frequently used as a backup
          > medium in streaming mode, but not exclusively.

          Another factor is blocksize, which may contain several records that are deblocked/gathered beforehand by software. Backups use LARGE block sizes to keep the tape in motion and maximize the ratio of data to IRG (inter record gap). Streaming tape drives evolved over time, such a the tiny square tapes that move directly from spool to spool. QIC drives were a logical progression: all tracks are erased on the first pass: that's why you can append but not re-write them (kinda like VHS: flying erase head vs. separate erase head).

          Tapes used in a random manner use one record per tape block, thus losing a lot of capacity to the space between records. DECtapes did that, as well as some Cipher QIC drives that emulated a floppy drive.

          Even ancient computers had scatter/gather, allowing the device to read/write data from non-contiguous RAM. Linux still has writev(2) and readv(2) regardless of hardware support for scatter/gather. The point being that it was possible to create large records on the fly even in RAM limited systems.

          I just happen to have my dad's IBM reference card right here:
          GX35-5001-0
          IBM System/360/370 reference data
          2401-2404, 2415 and 3420 magnetic tape units
          processing time by block size
          ... start citation ...
          MODES OF OPERATION

          continuous refers to operation where another command is issued immediately and the computing system data channel is locked up to the tape control unit while the IBG is traversed at full velocity

          start/stop refers to operation where the tape control is released from channel while the tape unit is stopping. The time to process a block includes only the time between access from zero velocity and disconnect from the channel.

          ... end citation

          That's part of why mainframes really rocked: the hierarchy of controllers and data channels allowed MANY concurrent I/O operations and queues/chains of commands operating without CPU intervention. Sridhar can probably construct Channel Control Words in his sleep :)

          > They were used as devices for data interchange

          I used to cut magtapes and pop them into express mail envelopes to mail to customers! In the early 90s, I bought my first QIC tape drive since that was the distribution medium for Unix (a stop-gap between floppy disks and CDs). It was common to see couriers carrying magtapes like oversized bangles along Wall Street.

          > For this reason, start-stop performance was very important for
          > high-end drives like the TU77 and TU78.
          > They have to start, stop, and
          > reverse direction, with minimal overshoot/undershoot, very quickly.

          Even before that, mainframes used TOS: Tape Operating System. Everything was optimized for tape operation, thus sequential or mostly-sequential methods such as ISAM (indexed sequential access method). Sorts were ingenious, using read-backwards when available. THOSE were the days of "real hackers"
        • David Gesswein
          ... The naval stuff I m familiar with is 3 phase delta. Aircraft is the most common usage for 400 Hz. 400 Hz gives weight/size savings.
          Message 4 of 23 , Aug 8, 2013
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            On Wed, Aug 07, 2013 at 11:23:00PM -0400, David Riley wrote:
            > Also, what do we have that runs on 400 Hz? We don't have much naval
            > equipment that I know of.
            >
            The naval stuff I'm familiar with is 3 phase delta. Aircraft is the most
            common usage for 400 Hz. 400 Hz gives weight/size savings.
          • David Riley
            ... I m working on a system with the Navy now that uses 400 Hz. Almost all the carrier stuff seems to, though perhaps it s because it interfaces with aircraft
            Message 5 of 23 , Aug 8, 2013
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              On Aug 8, 2013, at 7:56, David Gesswein <djg@...> wrote:

               

              On Wed, Aug 07, 2013 at 11:23:00PM -0400, David Riley wrote:
              > Also, what do we have that runs on 400 Hz? We don't have much naval
              > equipment that I know of.
              >
              The naval stuff I'm familiar with is 3 phase delta. Aircraft is the most
              common usage for 400 Hz. 400 Hz gives weight/size savings.

              I'm working on a system with the Navy now that uses 400 Hz. Almost all the carrier stuff seems to, though perhaps it's because it interfaces with aircraft equipment in a lot of cases.


              - Dave
            • B. Degnan
              ... When we rescued the UNIVAC 1219-II etc a lot of the power components were left behind, we ran out of time. The team to decommission the building was
              Message 6 of 23 , Aug 8, 2013
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                -------- Original Message --------
                > From: "David Gesswein" <djg@...>
                > Sent: Thursday, August 08, 2013 8:24 AM
                > To: midatlanticretro@yahoogroups.com
                > Subject: Re: [midatlanticretro] Re: Tape Drives
                >
                > On Wed, Aug 07, 2013 at 11:23:00PM -0400, David Riley wrote:
                > > Also, what do we have that runs on 400 Hz? We don't have much naval
                > > equipment that I know of.
                > >
                > The naval stuff I'm familiar with is 3 phase delta. Aircraft is the most

                > common usage for 400 Hz. 400 Hz gives weight/size savings.
                >

                When we rescued the UNIVAC 1219-II etc a lot of the power components were
                left behind, we ran out of time. The team to decommission the building was
                waiting outside waiting for us to finish removing the system. We did save
                some of the key power components. Given the 1219 system was a Navy system
                perhaps some of the power components we did save would be useful or "large
                enough". Of course this is all becoming a theoretical discussion.

                Bill
              • Evan Koblentz
                ... Of everything we own, I think it s safe to say the Univac is least likely to ever run. But ... never say never. :)
                Message 7 of 23 , Aug 8, 2013
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                  >> When we rescued the UNIVAC 1219-II

                  Of everything we own, I think it's safe to say the Univac is least likely to ever run. But ... never say never. :)
                • B. Degnan
                  ... to ever run. But ... never say never. :) ... If we had the correct power I really don t see why not. It s 100% intact and there was no damage that I know
                  Message 8 of 23 , Aug 8, 2013
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                    -------- Original Message --------
                    > From: "Evan Koblentz" <evan@...>
                    > Sent: Thursday, August 08, 2013 9:25 AM
                    > To: "MARCH Yahoo Midatlanticretro" <midatlanticretro@yahoogroups.com>
                    > Subject: Re: [midatlanticretro] Re: Tape Drives
                    >
                    > >> When we rescued the UNIVAC 1219-II
                    >
                    > Of everything we own, I think it's safe to say the Univac is least likely
                    to ever run. But ... never say never. :)
                    >

                    If we had the correct power I really don't see why not. It's 100% intact
                    and there was no damage that I know of to the machine to prevent a
                    console/lights type test at least. The entire system altogether, that's a
                    different story. In theory these are built to last I would not be
                    surprised if someone knowledgeable who had a couple of weeks to work on it
                    could get it up and running enough for a demo.

                    Bill
                  • Ray Sills
                    ... It s not just Navy, but much military equipment (especially airborne gear) uses 400 Hz, for the saving of weight and size of the components needed. One of
                    Message 9 of 23 , Aug 8, 2013
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                      On Aug 7, 2013, at 11:24 PM, Dave McGuire wrote:
                      >
                      > A lot of non-Navy gear requires 400Hz power. Most large Crays and
                      > CDC machines come to mind. Smaller inductors and capacitors in the
                      > power supplies.
                      >
                      > -Dave
                      >
                      > --
                      > Dave McGuire, AK4HZ
                      > New Kensington, PA
                      >

                      It's not just Navy, but much military equipment (especially airborne
                      gear) uses 400 Hz, for the saving of weight and size of the components
                      needed.

                      One of the reasons that the US uses 60 Hz AC mains power is that the
                      transformers to distribute the power are smaller than 50 Hz
                      transformers used in those countries using 50 Hz power. Another
                      meaning for "Big Iron". :)

                      73 de Ray
                    • tedheadster
                      I noticed that there was both a DEC TU78 and TU80 tape drive. I guess the TU80 is TS11 compatible? - Matthew
                      Message 10 of 23 , Aug 12, 2013
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                        I noticed that there was both a DEC TU78 and TU80 tape drive. I guess the TU80 is TS11 compatible?

                        - Matthew

                      • Dave McGuire
                        ... No. The TU80 is a relabeled CDC Keystone (92181 I think), the interface on which is of the two-connector Pertec formatted type. The TS11 uses a
                        Message 11 of 23 , Aug 12, 2013
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                          On 08/12/2013 12:41 PM, tedheadster wrote:
                          > I noticed that there was both a DEC TU78 and TU80 tape drive. I guess
                          > the TU80 is TS11 compatible?

                          No. The TU80 is a relabeled CDC Keystone (92181 I think), the
                          interface on which is of the two-connector Pertec "formatted" type. The
                          TS11 uses a DEC-proprietary serial bus, implemented for Unibus using an
                          M7982 controller board.

                          -Dave

                          --
                          Dave McGuire, AK4HZ
                          New Kensington, PA
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