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- Old AI-KA and OZ Tapes and What to Do with Them - How to copy 7 track tapes to remote 9 track tapes - ITS Tape-Saving Project
403 lines
16 KiB
Plaintext
Executable File
403 lines
16 KiB
Plaintext
Executable File
ITS Tape-Saving Project
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Project MAC, whence descended the AI Lab and LCS, developed a highly
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unusual operating system called ITS (Incompatible Timesharing System). For
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many years it was the only, or the chief, OS used at the labs, so most of
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the seminal work done here was done on machines running ITS. Full ITS
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first ran on the AI PDP6, and was ported to the DM PDP6. Later, PDP10s
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became available, and the labs acquired some of the earliest ones -- the
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AI-KA10 (AI Lab's machine), the ML KA-10 (used by the MathLab, Theory of
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Computation, Automatic Programming, and certain other LCS groups), and the
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DMS KA-10 (Dynamic Modeling Systems, also used by certain other LCS
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groups); these replaced the PDP-6s, which were slowly phased out. The
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well-known MACSYMA program was started on the AI-KA, moved to the ML-KA
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when that machine came online and there underwent much development, and
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finally needed some space to really run. At that point the Macsyma
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Consortium was established and bought MC, the first KL-10A installed
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outside DEC. MACSYMA continued to be upgraded on MC, as well as used by
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the many Macsyma Consortium customers, who often stored their data and
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special applications on the KL.
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After many years of overuse and under-maintenance, the latter generally
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performed by a small cadre of lab members who stole time from their other
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responsibilities to keep the machines going, the old ITS machines have
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slowly surrendered to the ravages of time, and gone the way of all silicon.
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The KAs were disposed of about four years ago. The KL, renamed MX in 1986,
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is reeling; while it was recently revived, its disk drives and memory boxes
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are in very bad shape, and we expect to dispose of it soon. The old ITS
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machines have been replaced by new, physically smaller, much more easily
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maintainable KS-10s (DEC-2020s), which sustain the ITS operating system
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(which, like the recently lamented Multics, contains many system features
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that are just now being discovered by the outside world), its atmosphere of
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cooperation in research, and what (after fifteen years) is still one of the
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best mail-delivery systems on the Internet.
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Why, when the old machines have been replaced by new hardware, is any
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comment needed? Because the AIKA, the MLKA, and the KL all had 7-track,
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800bpi (bits per inch) tape drives, and all their backup tapes were written
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on these drives. Even as early as the mid-1970s, 7-track drives were being
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superseded by 9-track drive technology; by now, 7-track drives are
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impossible to find. So the labs now possess a couple rooms full of backup
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tapes written at 7 tracks -- the tapes contain the labs' history, but due
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to the track difference, are unreadable on any hardware the labs now own or
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are likely to be able to get. Moreover, since the tapes were written at
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800bpi, they fill two rooms' worth of space, which the labs would prefer to
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put to more productive use.
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We want to preserve the labs' history, and free that space, by copying
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a certain subset of those tapes to modern format. For that reason, LCS has
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had the KL repaired one last time, so the old tapes can be read on its
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drive, and using available software, copied to the more modern format of 9
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tracks, 6250bpi. We propose to copy approximately one full dump per year
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per ITS, as well as all the GFR tapes (Grim File Reaper -- a rough
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equivalent of Twenex archiving); this should include on the order of 900
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old tapes, which will be copied onto 175-200 new tapes. When this project
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has been accomplished, the new tapes will contain most of the work done on
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the old ITS machines, and all the old 7-track tapes can then be disposed
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of. We realize that not everything will be saved, but this method of
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copying snapshots and GFRs should preserve most of the labs' important
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work.
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Concerning DM: for some reason, the DM-KA had a 9-track, 800bpi drive,
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so all its backup tapes were written in that format. As long as LCS
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maintains a similar format drive (suitable drives are now in use on XX),
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the DM tapes will be readable; a small program would need to be written to
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translate the data, but the ITS tape format is simple and well-documented,
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so such a project should be trivial for any competent systems programmer.
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Of course, when the labs consider disposing of their last drives which read
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9-track, 800bpi tapes, or when LCS wants to free the space currently used
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by the DM-KA tapes, a project like this one should be undertaken to
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preserve the DM history.
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Requirements:
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Time: Each tape takes about 10 minutes to copy, if everything goes
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well. However, due to tape age and in some cases frequent use, as well as
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machine and network trouble, problems do occur, so a safer estimate would
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be 15 minutes per tape. For 900 tapes, that translates as 225 hours of
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copying, or approximately 5 weeks' work for one person (at standard 40hr.
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weeks). With some competent assistance during hours when I am not
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available, this period might be halved. These estimates are based on Alan
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Bawden's work copying some of the MX GFR tapes to 1600bpi; since GFR tapes
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are by far the most abused ITS backups, the full dump tapes might not
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produce as many problems, but it is prudent to assume they will.
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Material: We need about 200 new 2400' tapes, of quality suitable for
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having data written at 6250bpi. A moderate quantity of documenting
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paraphernalia will be needed to label them all.
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Hardware: The MX-KL must keep running in at least as good shape as it
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currently does; it has the only available 7-track drive. The Chaosnet,
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specifically Subnet 6, the piece on which the ITS machines reside, must
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bear traffic well; it is the only way for the KL to send the tape data out.
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At least one of the AI Lab machines with 6250bpi tape drives (HERMES,
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VULCAN) must be usable, because they are the only sites the new tapes can
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be written. The LCS machine MILO has a 6250bpi drive but is not on the
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Chaosnet, and so is unusable for this purpose.
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Software: Already available; written by Dave Moon of Symbolics.
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People: Me, at full time or so for 3-4 weeks. Some effort from Ty and
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his crew when they are here but I'm not. Assistance at troubleshooting
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from Alan Bawden (AIL), John Wroclawski (LCS), and if necessary Dave Moon
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(Symbolics), to keep the hardware functional and solve any remaining
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software bugs.
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Possible other expenses: Tom Knight (AIL) has suggested that the new
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tapes, once written, should be copied (thus providing us 2 complete set of
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the snapshots and GFRs), and that one of these sets should be stored
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somewhere other than in NE43. Such copying can be done, he says, by
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outside firms for a relatively modest price. There is precedent for
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storing lab tapes offsite; for several years, many of the ITS backup tapes
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were stored in the old wind tunnel building; they were returned here when
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IPS (now IS) took over that space for its main computer facility.
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Magic fix for MX sysconsole going west:
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sys^H
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upc/
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^I
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^ -> PUSHJ P,UFLS
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^ -> SKIPL foo(I) ; inst. # 170457
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^I
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$$^R
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-1<return>
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pty^H
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:reatta CENT5/k
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12654
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print: 40685
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A prospective set of old ITS tapes to be copied
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Note that not all input tapes are full, and some may be unreadable. If a
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particular dump provides an excess of problems, we will have to use another
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nearby chronologically, and adjust the remainder accordingly. Any output
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tape used to finish copying a full dump will end up only partially full.
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Prefer using "Archive" dumps to "Full" dumps; on the other hand, prefer
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using tapes not marked as having been hit by the basement flood to those
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marked as so doused.
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The software does not allow splitting of input tapes onto output tapes;
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in other words, any input tape which runs off the end of the output tape
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it's being copied onto must be started again on a new output tape. We know
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that due to differences in inter-record gaps, 2 800bpi tapes sometimes fit
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onto one 1600bpi tape, and sometimes run over (requiring a second 1600bpi
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tape). We don't know what the 800-6250 ratio will be; division suggests
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that 7 old tapes will fit onto 1 new tape, but Dave Moon suspects that the
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inter-record gap diffence will allow only 5-6 old tapes per new one. The
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conservative ratio of 1:5 has been used in the table below; we might be
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able to do better, but should not count on it.
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To retain coherency among the new tapes, each full dump will be copied
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to a separate set; thus for each full dump, there will be one new tape only
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partially full, containing its last files. Tape is not expensive enough to
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subject future users of these tapes to the confusion that would result from
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jamming all tapes full without leaving these gaps. GFR tapes, however, can
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be copied as many as fit per tape.
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In the tables below, an input dump date preceded by * indicates an
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alternate to the previous dump. I use the most conservative number of
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output tapes needed for all sets of possible alternates. Note that ITS
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archive dumps are pretty much regular full dumps; originally there was an
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intent to save them longer or treat them as more sacred than ordinary full
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dumps, but this seems to have been washed away in the basement flood (in
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which many of the arch dump tapes were caught) if not earlier.
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Addendum: All tapes actually copied have been recorded in the copy logbook.
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The prospective lists below have also been altered to indicate tapes
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actually copied, up to the dashed lines; everything below them is still
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prospective and subject to change.
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Also, the old to new tape ratio is proving to be more like 4:1 than
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5:1. This varies depending on file size; also, some tapes are not full,
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and thus throw off this standard ratio.
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Also, all tapes marked ! are part of the time compromise. All such
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tapes are figured for a 4:1 compression ratio, although some will fit 5:1.
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AI-KA10 tapes
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input dump # output
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date tapes #s # tapes type tapes
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Apr 71 1000-1003 4 first arch 1 ; may have been missing
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; last tape
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Apr 72 1037-1044 8 arch 2
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Mar 73 1062-1070 9 arch 2
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Dec 73 1087-1094 8 arch 2
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Dec 74 1108-1120 13 arch 3
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Dec 75 1172-1188 17 arch 4
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Dec 76 1210-1235 26 arch 6
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Dec 77 1266-1300 34 arch 7 ; there is no tape 1280
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!Aug 79 2459-2492 34 full 8
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!May/Jun 81
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2804-2846 43 full 9
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Aug 82 3046-3085 40 last full 9
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---------------------------------------- total 53 tapes actually made
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Dec 78 1336-1366 31 arch
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*Jan 79 2320-2349 30 full 7
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Dec 79 1409-1448 40 arch
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*Feb-Mar 80
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2558-2595 38 full 8
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Nov 80-Jan 81 ; incomplete dump
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2767-2803 38 full 8
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; perhaps move back to summer/fall '80 dump
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GFRs: 1264, 1265, 1301, 1334, 1335, 1367, 1407, 140, GFR1-GFR11, GFR13-GFR27
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GFR30-GFR32
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yearly full or archive dumps 269 input tapes 58 output tapes
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first and last fulls 57 12
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GFR tapes 36 8
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--- --
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total 362 78
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ML-KA10 tapes
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input dump # output
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date tapes #s # tapes type tapes
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Jun 73 1032-1036 5 arch 1
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Jun 74 1050-1055 6 arch 2
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Jul 75 1074-1079 6 arch 2
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Apr 76 585-593 8 full 2
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Apr 77 678-688 11 full 3
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!Jan 79 851-865 15 full 4
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!May 80 2040-2053 14 full 4
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!Jan 82 2202-2217 16 full 4
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Sep 83 2435-2450 16 last full 4
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---------------------------------------- total 26 tapes actually made
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Apr 78 770-781 12 full 3
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Apr 79 894-907 16 full 4
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Apr 80 2025-2039 15 full 4
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Apr 81 2131-2144 14 full 4
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Apr 82 2231-2246 16 full 4
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Mar 83 2385-2402 18 full 5
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GFRs: 154, 163, 165, 167-169, 171, 174-177, GFR180-190, GFR192-199,
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GFR1-13, GFR15-29
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yearly full or archive dumps 129 input tapes 28 output tapes
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last full 16 4
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GFR tapes 58 12
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--- --
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total 203 44
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MC-KL10 tapes
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input dump # output
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date tapes #s # tapes type tapes
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Jan 76 500-510 11 full 3
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Dec 76 603-618 16 full 4
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Dec 77 1029-1048 20 arch 4
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!Jun 79 2013-2029 17 full 5
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!Oct-Dec 80
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2405-2447 43 full 10
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Aug 82 2870-2927 58 full 13
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; Last Whole Macsyma Dump
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---------------------------------------- total 39 tapes actually made
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!Jul 84 3367-3421 55 full 14
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----------------------------------------
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Dec 78 1067-1084 18 arch 4
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*Jan 79 944-961 18 full 4
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Dec 79 1085-1114 30 arch 6
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*Jan 80 2131-2159 29 full 6
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Oct 80 2405-2447 43 full 9
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*Mar 81 2448-2490 43 full 9
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Nov 81 2662-2706 45 full 9
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*Jan-Feb 82
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1153-1204 52 last arch 11
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Aug 83 3144-3196 53 full 11
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*Nov 83 3197-3259 63 full 13
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Aug 85 3821-3874 54 full 11
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*Oct 85 3875-3927 53 full 11
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[Oct 86 4100-4122, last full dump, was run at 9-track, 1600 bpi, so does
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not need to be copied, merely saved.]
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GFRs: 175-199, GFR1-68, GFR70-88
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yearly full or archive dumps 411 input tapes 85 output tapes
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first and last archives 64 14
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GFR tapes 102 26
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--- --
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total 577 125
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GFR tape schedule
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AI
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1264 -- 22aug77 GFR6 -- 29oct80 GFR19 --
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1265 -- 16nov77 GFR7 -- 3nov80 GFR20 --
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1301 -- 2apr78 GFR8 -- 26nov80 GFR21 --
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1334 -- 8aug78 GFR9 -- 12dec80 GFR22 -- 13feb82
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1335 -- 24nov78 GFR10 -- 28jan81 GFR23 --
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1367 -- 14feb79 GFR11 -- 24may81 GFR24 --
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1407 -- 12oct79 GFR13 -- 25aug81 GFR25 --
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140 -- 3dec79 ? GFR14 -- 4oct81 GFR26 --
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GFR1 -- 15jul80 GFR15 -- 18oct81 GFR27 -- 28jan83
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GFR2 -- 26aug80 GFR16 -- 15nov81 GFR30 -- 28jan83
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GFR3 -- 26aug80 GFR17 -- 6jan82 GFR31 -- 28jan83
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GFR4 -- 26sep80 GFR18 -- 6jan82 GFR32 -- 28jan83
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GFR5 -- 13oct80
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ML
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154 -- 23dec73 GFR189 -- GFR10 --
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163 -- 28oct74 GFR190 -- GFR11 --
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165 -- 21dec74 GFR192 -- GFR12 --
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167 -- 13mar75 GFR193 -- GFR13 --
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168 -- 24jun75 GFR194 -- GFR15 --
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169 -- 25sep75 GFR195 -- GFR16 --
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171 -- 13oct75 GFR196 -- GFR17 --
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174 -- 2jun76 GFR197 -- GFR18 --
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175 -- 20jul76 GFR198 -- GFR19 --
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176 -- 15aug76 GFR199 -- GFR20 --
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177 -- 30aug75 GFR1 -- GFR21 --
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GFR180 -- GFR2 -- GFR22 --
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GFR181 -- GFR3 -- GFR23 --
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GFR182 -- GFR4 -- GFR24 --
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GFR183 -- GFR5 -- GFR25 --
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GFR184 -- GFR6 -- GFR26 --
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GFR185 -- GFR7 -- GFR27 --
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GFR186 -- GFR8 -- GFR28 --
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GFR187 -- GFR9 -- GFR29 --
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GFR188 --
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MC
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175 -- 23may77 GFR14 -- 18mar80 GFR51 -- 17mar83
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176 -- 7sep77 GFR15 -- 2apr80 GFR52 -- 2may83
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177 -- 28oct77 GFR16 -- 20apr80 GFR53 -- 24jun83
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178 -- 27nov77 GFR17 -- 2may80 GFR54 -- 28jul83
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179 -- 25jan78 GFR18 -- 14may80 GFR55 -- 18aug83
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180 -- 14mar78 GFR19 -- 22may80 GFR56 -- 18nov83
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181 -- 6apr78 GFR20 -- 23oct80 GFR57 -- 28dec83
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182 -- 11may78 GFR21 -- 6nov80 GFR58 -- 11feb84
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183 -- 8jun78 GFR22 -- 11dec80 GFR59 --
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184 -- 11jul78 GFR23 -- 1jun81 GFR60 --
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185 -- 20jul78 GFR24 -- 29jan81 GFR61 --
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186 -- 17aug78 GFR25 -- 12feb81 GFR62 -- 11mar84
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187 -- 8sep78 GFR26 -- 12mar81 GFR63 -- apr84
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188 -- 18sep78 GFR27 -- 31mar81 GFR64 -- may84
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189 -- 25sep78 GFR28 -- 9may81 GFR65 -- 28may84
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190 -- 16oct78 GFR29 -- 2jun81 GFR66 --
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191 -- 28oct78 GFR30 -- 15jun81 GFR67 --
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192 -- 11nov78 GFR31 -- 17jul81 GFR68 --
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193 -- 27nov78 GFR32 -- 3aug81 GFR70 --
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194 -- 9dec78 GFR33 -- 13aug81 GFR71 --
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195 -- 20dec78 GFR34 -- 21aug81 GFR72 --
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196 -- 5jan79 GFR35 -- 3sep81 GFR73 --
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197 -- 31jan79 GFR36 -- 3oct81 GFR74 --
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198 -- 18feb79 GFR37 -- 18oct81 GFR75 --
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199 -- 23mar79 GFR38 -- 11mar82 GFR76 --
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GFR1 -- 10apr79 GFR39 -- 3apr82 GFR77 --
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GFR2 -- 26apr79 GFR40 -- 15may82 GFR78 --
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GFR3 -- 4may79 GFR41 -- 19may82 GFR79 --
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GFR4 -- 7jun79 GFR42 -- 9jul82 GFR80 --
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GFR5 -- 2jul79 GFR43 -- 3aug82 GFR81 --
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GFR6 -- 21jul79 GFR44 -- 8sep82 GFR82 --
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GFR7 -- 31jul79 GFR45 -- 5oct82 GFR83 --
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GFR8 -- 11aug79 GFR46 -- 30oct82 GFR84 --
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GFR9 -- 23aug79 GFR47 -- 15dec82 GFR85 --
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GFR10 -- 10sep79 GFR48 -- 23dec82 GFR86 --
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GFR11 -- 18jan80 GFR49 -- 3jun83 GFR87 --
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GFR12 -- 10feb80 GFR50 -- 6feb83 GFR88 --
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GFR13 -- 22feb80
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