Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ico!ism780c!news
From: news@ism780c.isc.com (News system)
Newsgroups: comp.arch
Subject: Re: What is a Mainframe?
Message-ID: <30606@ism780c.isc.com>
Date: 28 Jul 89 20:23:37 GMT
References: <355@torsqnt.UUCP> <3490016@wdl1.UUCP>
Reply-To: marv@ism780.UUCP (Marvin Rubenstein)
Organization: Interactive Systems Corp., Santa Monica CA
Lines: 32

In article <3490016@wdl1.UUCP> bobw@wdl1.UUCP (Robert Lee Wilson Jr) writes:
>And note that the tube type machines from which the 709x evolved were also
>36 bitters, and in turn that 36 is a nice multiple of 12 which is the
>number of rows in an "IBM" card. Since old machines like the 704/701 read
>cards as binary images into core, and translated bit patterns into
			     ^^^^
If memory serves, the 701 was not a core machine.  The 704 was the first
IBM machine with core.

>(EBCDIC) characters via internal software rather than something in an I/O
>channel, this was not a coincidence!
>The past marches on!
>Bob Wilson

Actually the 701/704/709/7090/7094 read cards row wize. that is the contents
of row 9 was read then the contents of row 8 and etc.  And since there were
36 bits to the word, only 72 colums of a card were be read.  The "not a
coincidence" is the fact that FORTRAN lines are limited to 72 characters.

The choice of 36 bits for the word size has nothing to do with the 12 bits
per card column.  My guess is that 36 bits of precision was percieved to be
required for scientific computation.

Bob is correct in that translating card images (as an array of bits) into
characters was done by software.  The operation was refered to as corner
turning.  When I was with Standard Computer Co. I built an emulator for teh
IBM 704/709 family.  Our card readers read all 80 columns of a card a column
at a time.  So the card read firmware threw away 8 columns and did a corner
turn so that the 709 software could turn it back!


   Marv Rubinstein - IBM 709/7090 maven