🚀 go-pugleaf

In a recent article jje@virtech.uucp (Jeremy J. Epstein) writes:

>What were the advantages/disadvantages of 7 track as opposed to
>9 track?
   Compatibility with existing tapes.  Beyond that, nothing.

>BTW, the 9 track drive had low, medium, and high densities in those
>days: 200 BPI, 556 BPI, and 800 BPI.  1600 and 6250 hadn't even
>been thought of...

   Nope.  The 200/556/800 BPI densities were for 7-track tape.  The 
   original 9-track tapes were all 800 bpi, with 1600 bpi and 6250
   arriving later.  One real advantage of specifying 9-track tape
   is that the tape drive senses the density of a tape automatically,
   so you don't have to specify the density when using a drive
   capable of more than one density.  Also, 9-track tape is *always*
   written in odd parity, so you don't have to specify that option.
   One real pain in 7-track days was having to be able to handle a
   tape with some records in even parity and some in odd.  At least
   I never had to work with a tape in more than one density...

Joe Morris

In article <1990Oct3.2...@hq.demos.su> a...@hq.demos.su (Vadim G. Antonov) writes:
 > In article <1990Oct03.172748.18683@virtech.uucp> jje@virtech.uucp (Jeremy J. Epstein) writes:
 > >What were the advantages/disadvantages of 7 track as opposed to
 > >9 track?
 > Hmmm... Obviously you can not write whole bytes to 7 track tape (yes,
 > actually you can - after a clever hack :-).
Oh, but in the days of 7 track tape you could write a byte plus parity.
It is only with the introduction of the 360 that IBM proclaimed that from
that time onward a byte would be 8 bits.  And for some reason everybody
followed.  (Yes, also IBM has known 6 bit bytes!)
--
dik t. winter, cwi, amsterdam, nederland
d...@cwi.nl

You Bet!  We have a working 7-track drive, used to read a WHOLE
ARCHIVE of 7-track radar data tapes....recorded back as far as
the mid-60's.  But, it's slowly being converted to 6250 9-track
(the 7-track machine has to be cleaned every 1 or 2 tape reads)
and each 7-track is read multiple times and compared for differences
(error checking!).  Only hope that the majority gets converted
before the drive gives out...tough to get service on old 7-track eqpt.



Monte Bateman (WB5RZX @ WB5RZX)
bateman @ nsslsun.gcn.uoknor.edu
National Severe Storms Laboratory, Norman, OK!  73069

jje@virtech.uucp (Jeremy J. Epstein) writes:

>When I started using the IBM 360 mainframe at the University of
>New Mexico, they still had a 7 track tape drive which was around
>for reading obsolete tapes.
...
>BTW, the 9 track drive had low, medium, and high densities in those
>days: 200 BPI, 556 BPI, and 800 BPI.  1600 and 6250 hadn't even
>been thought of...

By the way, the 7 track tape drives had a translator and a convertor and
sometime you had to try all the four combination of translator ON/OFF and
converter ON/OFF - what ever that was.

At that time the University of Bonn had a 7090 and a 1410 as spooling machine
(and not to forget Mr. Petri as director!). I was responsible for an additional
360 Model 50. But on warm summer days the 360 should be switched off to let
the 7090/1410 run. So I had to write a spooling program running on the 360,
reading cards in BCD and column binary and writing them whit translator ON or
OFF and convertor OFF or ON (or vice versa:-?) to 7-track tape.
-- 
Werner Icking          ick...@gmdzi.gmd.de          (+49 2241) 14-2443
Gesellschaft fuer Mathematik und Datenverarbeitung mbH (GMD)
Schloss Birlinghoven, P.O.Box 1240, D-5205 Sankt Augustin 1, FRGermany

In article <10...@n3dmc.svr.md.us> jo...@n3dmc.svr.md.us (John Limpert) writes:
>
>Who needs bytes?  Real computers used 6 bit field code, 7 bits after
>parity was added.
>
Right. That what was used on BESM-6 (48 bit word).

What about RADIX-50? ( 5 1/3 bit coding ;-)

-- 
Dmitry V. Volodin <d...@hq.demos.su>     |
fax:    +7 095 233 5016                 |      Call me Dima (D-'ee-...)
phone:  +7 095 231 2129                 |

jje@virtech.uucp (Jeremy J. Epstein) writes:

>Just curious...does anyone still have a working 7 track drive?
>What were the advantages/disadvantages of 7 track as opposed to
>9 track?

If you only got 6 bit characters, you only need...

Which also explains all the wierd byte formats you could/can write
to 9-track tapes. They try to fit 6 and 9 bit chars onto 8 bits of 
tape without wastage.


--

------------         -----------------     ---------------------
Mark Delany          ma...@Aus.Sun.COM     ...!sun!sunchat!markd
------------         -----------------     ---------------------

ick...@gmdzi.gmd.de (Werner Icking) writes:
>By the way, the 7 track tape drives had a translator and a convertor and
>sometime you had to try all the four combination of translator ON/OFF and
>converter ON/OFF - what ever that was.

Hmmm. Was this where NRZI first originated? Of course we *all* know that
NRZI is new-fangled stuff. The precurser being RSI. Was there a 
pre-pre-curser? 

BTW. NRZI means Non-Return-to-Zero-Inverted - tape-drives didn't like
runs of zero bits.

--

------------         -----------------     ---------------------
Mark Delany          ma...@Aus.Sun.COM     ...!sun!sunchat!markd
------------         -----------------     ---------------------

In article <22...@charon.cwi.nl> d...@cwi.nl (Dik T. Winter) writes:
*
*  > In article <1990Oct03.172748.18683@virtech.uucp> jje@virtech.uucp (Jeremy J. Epstein) writes:
*  > >What were the advantages/disadvantages of 7 track as opposed to
*  > >9 track?
*  > Hmmm... Obviously you can not write whole bytes to 7 track tape (yes,
*  > actually you can - after a clever hack :-).
*
* Oh, but in the days of 7 track tape you could write a byte plus parity.
* It is only with the introduction of the 360 that IBM proclaimed that from
* that time onward a byte would be 8 bits.  And for some reason everybody
* followed.  (Yes, also IBM has known 6 bit bytes!)
*
Welll...
--
7-track was designed to accommodate the 6-bit "BCD" or "Field
Code" character/byte, plus a parity bit.  It really had nothing to do with
the number of heads which could be spread across the tape.
--
9-track was designed to accommodate the 8-bit "EBCDIC" character/byte, plus
a parity bit.
--
"Data Translation" applied to 7-track tapes on systems with 8-bit bytes:
it simply swapped 6-bit vs. 8-bit character codes.  Of course, it limited
the 8-bit code to only the 64 EBCDIC characters corresponding to the
original BCD character set.  I disremember what it did when told to
do 8-to-6 for an EBCDIC code outside the nominal map.
--
"Data Conversion" took three 8-bit codes (24 bits) from the system and did
them as four 6-bit codes on tape.
--
Yes, it was/is possible (at least on IBM drives of the era) to turn on
both Translation and Conversion, but I can't recall which was done first
or what the real result was.  I do remember that most folk regarded the
combination as spectacularly unuseful.
-------------
regardz,
Ken

> Just curious...does anyone still have a working 7 track drive?
> What were the advantages/disadvantages of 7 track as opposed to
> 9 track?
> 
  Gee, doesn't everyone have a few 7-track drives on the
new machines just to read all those old 7 track tapes...
Willy

In <122...@linus.mitre.org> jcmo...@mwunix.mitre.org (Joe Morris) writes:


>   tape with some records in even parity and some in odd.  At least
>   I never had to work with a tape in more than one density...

>Joe Morris

Lucky bastard, I remember an archiving system in use on our 6600 way
back in '75 or so on our 7-track 200/556/800 drives that routinely
used different densities on a single tape.  I think it recorded the
directories at high (556) density, while the files themselves were at
200BPI for reliability.  Just about as bizarre as it gets.

Yeah, those were the days.  I once destroyed the hub on a CDC drive by
neglecting to tighten it down on the tape reel.  Chunks of plastic were
flying everywhere.

--
Gregory R. Travis                Indiana University, Bloomington IN 47405
Chief Pilot			 Flight Department
gr...@cica.cica.indiana.edu       Center for Innovative Computer Applications

In article <122...@linus.mitre.org>, jcmo...@mwunix.mitre.org (Joe Morris) writes:
>    One real pain in 7-track days was having to be able to handle a
>    tape with some records in even parity and some in odd.  At least
>    I never had to work with a tape in more than one density...

  A "feature" of the DEC TM02 tape formatter (some still in use today) is
that it will gleefully change density when told to (between 800 and 1600,
or course 8-). Now, the fine folks at ANSI have decreed that this is a
definite no-no and all that, so (rather than fix the hardware) the various
and sundry DEC operating systems that support this formatter now check to
see if the BOT bit is set before accepting a set density command.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	te...@spcvxa.spc.edu	(201) 915-9381

  All this about 7track tapes takes me back to when I started in this
business, and there were 3/4" tapes, on 10 inch aluminium reels.  I
*think* they were the original 7 track tapes, but I kinda remember
talk back then (1972-3) about 2 inch tapes having been used in the
early 50s.
  Anyone else remember these nowadays "oversize" tapes?

BTW- those hummers were a real *joy* to mount -- it was all manual, with
you the operator having to stuff the tape down the vacuum tape wells, bang
on the reels to ensure that they were sealed/secure, hit the *ready* buttons,
start the reel spinning, and jump back before you lost a finger or two...
Now THOSE were the days when an operator really could have gone and asked
for hazard duty pay and maybe gotten it... 
 (I won't even mention what happened one time when a reel wasn't firmly
  mounted and went into high-speed rewind....)

Oh, yes, I remember the 3/4" tapes on both the Burroughs 220 and the Honeywell
800.  The 220 tapes had two "lanes" of data, that is, were logically organized
like two tapes side by side.  The 800 tape drives had vacuum hub clamps, and
occasionally you couldn't get one of the damn things to let go of the reel.
This was more serious than it sounds, for in batch processing every idle
second was money down the drain.

The most picturesque of the 3/4" handlers that I encountered were the
Burroughs Datafiles, a.k.a. the "Datafail."  These were 3/4" tape
loops in large bins (they looked like mummy cases lined against the
wall) without vacuum tensioners; the tape would pick up a static
charge and wrap around the capstan with dire results ...

In article <122...@linus.mitre.org>, jcmo...@mwunix.mitre.org (Joe Morris) writes:
>
>    Also, 9-track tape is *always*
>    written in odd parity, so you don't have to specify that option.
>    One real pain in 7-track days was having to be able to handle a
>    tape with some records in even parity and some in odd.  
>
  Hmmm...
    We still have many 7 track tapes lying about that were written
with headers in even parity BCD, and data records odd parity binary.

    Just try writing binary data on a 7-track tape in even parity...

WIlly

In article <122...@linus.mitre.org>, jcmo...@mwunix.mitre.org (Joe Morris) writes:
     Also, 9-track tape is *always*
     written in odd parity, so you don't have to specify that option.

This isn't strictly true of all drives.  My first Unix machine, a
Perkin-Elmer running Wollongong v6 (as opposed to Bell Labs v6, whose C
compiler grew the stack in the other direction), had a tape drive (actually
I think the controller specifies this) that always wrote even parity, and
ignored (!) parity on reads.  Our Vax 11/780 with TU-58 drives refused to
read tapes with even parity.  So I translated them on a pdp-11 that always
wrote odd parity but would sense parity on reads, and switch to whatever
parity was used to write the tape.

Remember DECtape?  18 tracks, 3/4 inch wide.  Half the tracks were redundant
copies of the other half.

In article <38...@cos.com> fetter@cos.UUCP (Bob Fetter) writes:
>
>  All this about 7track tapes takes me back to when I started in this
>business, and there were 3/4" tapes, on 10 inch aluminium reels.  I
>*think* they were the original 7 track tapes, but I kinda remember
>talk back then (1972-3) about 2 inch tapes having been used in the
>early 50s.
>  Anyone else remember these nowadays "oversize" tapes?

Back in the early 60's, there were 1" tapes on 10" aluminum reels.  No
vacuum columns; instead there were servo arms.  They were referred to as
Potter-Brumfield (or something like that).  The interesting thing about these
tapes were that they would be performatted into blocks, just like a disk.
Each block was consecutively numbered, and the data portions of the block
were rewritable.  The controller that went with them could accept a command
of the form "Slew forward/backward N blocks", so you could use these as
random access devices, albeit with enormous latency times.  And we did!
The monitor [kernel] was responsible for ensuring that tape motion commands
were far enough apart so that you couldn't snap the tape.

Russ Herman
UUCP: ..uunet!attcan!ontmoh!rwh

>ignored (!) parity on reads.  Our Vax 11/780 with TU-58 drives refused to
>read tapes with even parity.

I'll bet you had fun stuffing those .5" reels into those little cartridges.
(Okay, okay, you just confused the drive.  I'll bet you meant "tu78".  The
tu58 was DECtapeII -- little cartridges like found on 750's.

>Remember DECtape?

Sure do.  I've got several score of them that I can't bear to part with,
despite the fact that I have no drives.

>  18 tracks, 3/4 inch wide.  Half the tracks were redundant
>copies of the other half.

Block-addressable, too.  People actually ran RT11 with DECtape (of either
vintage) as their system device.  Strange but true.  Stranger and more rare
was the TA11/TA90 (I think it was 90..) -- 96k on an audio cassette.  Yes,
you could run RT11 with that as your system device (you got two drives in
each box).  I've actually seen a set of RT11 V1 DECcassettes.  These seem to
have been packaged with low-end 11/10's for lab stuff.

--

da...@convex.com (in case sendmail screwed up the headers)

In article <1990Oct8.1...@sctc.com>, boe...@sctc.com (Earl Boebert) writes:
> The most picturesque of the 3/4" handlers that I encountered were the
> Burroughs Datafiles, a.k.a. the "Datafail."  These were 3/4" tape
> loops in large bins (they looked like mummy cases lined against the
> wall) without vacuum tensioners; the tape would pick up a static
> charge and wrap around the capstan with dire results ...

  Does anyone remember the IBM "Data Cell"? It was introduced around the
same time as the 360, as I recall. Imagine a cross between flypaper and
a tie rack 8-). It used long strips of (maybe) 2" tape and would go fondle
the desired strip onto the read/write station on demand (or maybe after
being repaired). Standard procedure was to read the full tape set once per
shift, or the beast would start sticking with disastrous results.

	Terry Kennedy		Operations Manager, Academic Computing
	terry@spcvxa.bitnet	St. Peter's College, US
	te...@spcvxa.spc.edu	(201) 915-9381

In article <106...@convex.convex.com> da...@convex.com (Anthony A. Datri) writes:
>>Remember DECtape?
>Sure do.

I've even have one DECtape... but unfortunately there are no devices
I can mount it on :-( . I used it on old 11/40 as my archive DISK :-)
under RT-11.

>Strange but true.

The first direct-access :-) tape I've seen was the 1/2" tapes of BESM-6.
It contains 1000 (octal :-) 1K word zones (each word is 6 bytes long).
One should format tape before using. Moreover operating system DISPAK
allows users to use tapes instead of disks and vice versa :-).

I was *very* surprised when I discovered block-oriented tapes in Unix.
These funny special files are still alive and working. :-) Thus I see
no problem in writing DECtape driver for Unix.

>Stranger and more rare
>was the TA11/TA90 (I think it was 90..) -- 96k on an audio cassette.  Yes,
>you could run RT11 with that as your system device (you got two drives in
>each box).  I've actually seen a set of RT11 V1 DECcassettes.  These seem to
>have been packaged with low-end 11/10's for lab stuff.

Gee! The Soviet clone for this device is called CT-1. Our SM-4 (11/34)
had such a device but it was always broken. The only thing I've done
with this device - I wrote Unix kernel to it and played it back on
cassete audio player. Sounds nice. :-)
(Just imagine an ugly large boxes equipped with cassete tape drives! :-)

Curiousily but this device is still in mass-production :-) A new Soviet
clone of VAX-11/730 :-) (SM-1700) is equipped with a pair of such beasts.

	Vadim Antonov
	DEMOS, Moscow, USSR
	(It is a joke!)

In article <1990Oct3.2...@hq.demos.su>, a...@hq.demos.su (Vadim G. Antonov) writes:
> In article <1990Oct03.172748.18683@virtech.uucp> jje@virtech.uucp (Jeremy J. Epstein) writes:
> >What were the advantages/disadvantages of 7 track as opposed to
> >9 track?
> 
> Hmmm... Obviously you can not write whole bytes to 7 track tape (yes,
> actually you can - after a clever hack :-). 9 track tape provides some
> useful features like parity checking and tape markers...


As I always understood it, the predecessor to 7 bit ASCII was a 6 bit
character code. I think it had the middle 64 characters out of the 7 bit set.
The 7 bit ASCII code wasn't formalized until around 1965/66. 

Hence there were many machines with word sizes that were a multiple of 6 bits 
in the '60s, 12, 18, 36, 60. These word sizes were useful for storing symbol 
names e.g. 6 character FORTRAN symbols in one 36 bit word.

I would guess that 7track tape was also designed for one 6 bit character per
frame + parity.

Does this sound reasonable?
-- 
Anthony Shipman                               ACSnet: a...@bohra.cpg.oz.au
Computer Power Group
9th Flr, 616 St. Kilda Rd.,
St. Kilda, Melbourne, Australia
D

In article <1990Oct10....@hq.demos.su>, a...@hq.demos.su (Vadim G. Antonov) writes:
> Curiousily but this device is still in mass-production :-) A new Soviet
> clone of VAX-11/730 :-) (SM-1700) is equipped with a pair of such beasts.

Gosh! What a coincidence! My official DEC /730 uses a pair of TU58 cassettes
as a console media.

When the 8700/8800 series gets cloned, will the Pro350 be cloned for the
console device? :-)
-- 
===============================================================================
Roger Ivie

35 S 300 W
Logan, Ut.  84321
(801) 752-8633
===============================================================================