[GreenKeys] Model 29 ASR

Wed Aug 17 17:15:20 EDT 2016

probably EBCDIC, as  a  spectrum 70  tried to be an IBM  360....

Ed# _www.smecc.org_ (http://www.smecc.org)  

In a message dated 8/17/2016 1:20:56 P.M. US Mountain Standard Time,  
73131.3073 at compuserve.com writes:

Years ago I had a Model 35 KSR that  was the control console for an RCA 
Spectra 70 computer system. It was painted  in the white and baby blue colors 
of that system and had the big round RCA  logo on it. It was definitely NOT 
at ASCII machine but rather BCD or EBCDIC, I  don't know which.

Tim Swarthout, WA5QEG

-----Original  Message-----
From: Jim Haynes <jhhaynes at earthlink.net>
To: ralph  irish <w8roi at wowway.com>
Cc: greenkeys  <greenkeys at mailman.qth.net>
Sent: Wed, Aug 17, 2016 10:51  am
Subject: Re: [GreenKeys] Model 29 ASR

When I was living in the  Chicago area I got a couple of machines by way
of Michigan Bell, but I  don't remember how it was arranged. Probably
Bert Prall had something to do  with it.

One of these, which I still have, was the Delta Airlines  version of the
28ASR which I have written about several times in the past.  The other
I don't remember if I got the whole ASR or just the cabinet, but  it was
one of the "pink" cabinets like Model 29s were made in. I  converted
that to an 8-level machine using Model 35 parts. I never did like  the
Model 35 cabinet anyway, and this one I just repainted dark brown  and
put the M35 stuff inside. (As they say of certain artists, this is  when
I was in my Dark Brown phase.)

The Model 29 as we know it was  not EBCDIC; it was 6-level IBM BCD code,
a forerunner of EBCDIC to be sure,  but only 6-level and upper case only.
As you have no doubt read it was  originally developed as a 6-level
up/low case machine to replace the Model  20 in Teletypesetter service,
but apprently nobody wanted to buy any.  (Marketing goof on Teletype's
part, I guess. By then hot metal typesetting  and Teletypesetter were
on the way out.) So it was reworked a little with  the IBM BCD code for
internal Bell System use in data processing. It was  officially called
the Model 28 Integrated Data Processing set. Bell didn't  want any of them
to escape into the world at large. One reason I'm told is  that it would
seem they were playing favorites with IBM and ignoring the  other computer
companies which had slightly different versions of the BCD  code. That
reason seems bogus, because it would be trivial to modify it for  some
other BCD code. The more substantial reason was that development  of
ASCII was under way and Bell didn't want anything that would compete  with
ASCII to get out there; they wanted to insure that ASCII would be the  one
standard. In the meantime the military had Fieldata and I believe  that
was what got used in AUTODIN, though no Fieldata teleprinters  were
released - AUTODIN came with an electronic box that could convert  Baudot
or BCD to its own transmission code.

EBCDIC was a late-comer  in the code development. During the development
of ASCII, IBM kept putting  up objections that were unacceptable to the
other companies participating  in the standard development. The main point
of contention is that Hollerith  punched-card code has some gaps in the
alphabet, with other characters in  the gaps. BCD does also because it
is really just a simple translation from  Hollerith. And IBM considered
this so important that they wanted to require  any new standard code to
retain the property. In this they were wrong,  since 512 bytes of memory
would provide conversion tables between any two  8-level codes and there
is no real need for a conversion that can be done  by trivially simple
logic. But IBM has always had a penchant for solving  the problems of
the previous generation of equipment, like they say the  generals are
always fighting the previous war. The good guys insisted there  should be
no breaks in the alphabet, so that sorting would not be upset by  the
funny characters in the middle. So ASCII had to have an unbroken  series
of binary numbers representing A through Z.

IBM surprised  everyone by suddenly withdrawing their objections to ASCII,
and the  standard was adopted. Then IBM announced their new System/360
computer line  and EBCDIC. EBCDIC has the breaks in the alphabet that
they wanted. I  assume IBM thought they could use their dominant marketing
position to  establish EBCDIC as a de facto standard and that ASCII would
then wither  away, with only some legacy services such as TWX using it.
Since the U.S.  government required ASCII in all its computer systems
thenceforth, IBM put  an ASCII mode bit into System/360, which made some
very minor change to the  way the system operated, and which was so
unimportant that it was dropped  from System/370.

I believe what turned the tide in favor of ASCII was  the Model 33. Not
in its intended role as a TWX terminal, but in the  totally new role of
a computer remote terminal and minicomputer console  device. The
minicomputer and time-sharing businesses had no need for  punched card
input; and there was nothing to compete with the Model 33 in  DataPhone
service as a remote terminal, nor hardwired to the computer as a  local
console. What we now call the mainframe computer companies really  had
no means of attaching cheap start-stop terminals to their systems;  they
preferred schemes in which a single terminal adapter polled  multiple
terminals on the same line for  messages.
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