From: +ACI-W. J. Metzger+ACI- +ADw-w.metzger+AEA-HEF.RU.NL+AD4-
Sent: Thursday, April 06, 2017 7:47 PM


+AD4- And before it introduced the 6600 with 60 bit words, CDC also had some
+AD4- 48-bit models.  

When introduced in 1951, the fastest machine in the world, the Pilot ACE,
had 32-bit words, and was used for scientific work.

+AD4- In Robin's time frame IBM's top 'scientific' machine was the 709, 7090
+AD4- with 36-bit words.

(hence the 72 columns for programs a la FORTRAN)

From the 1955, the top English scientific machines had 32-bit words.

+AD4-  Their top 'business' machine was the 7070, which was
+AD4- decimal, not binary, with words of 10 decimal digits,an exponent range
+AD4- in floating 10+AF4--49 - 10+AF4-49 and a fraction of 8 decimal digits.  IBM then
+AD4- combined their business and scientific lines into one line with the
+AD4- introduction of the 360 series (late 70s if I recall well), which
+AD4- introduced the 32-bit word. 

The S/360 was delivered in 1966, maybe 1965. 

+AD4- Pre IBM360, DEC had introduced 'mini'-computers.  The earliest, the
+AD4- PDP-1, had an 18-bit word (note - half of the word length of the current
+AD4- IBM 7090), but no floating point, at least not on the basic computer --
+AD4- perhaps there was an option.

Other machines of the early 1960s had 48-bit words.

+AD4- In this timeframe characters were represented by 6 bits (bi-octal)
+AD4- allowing only 64 characters, a major limitation for business machines.

The S/360 had 64 characters, eminently suitable for commercial work.

+AD4- Note that the IBM 7070 used bi-decimal, allowing 100 characters.  I
+AD4- suspect that the character limitation was a major reason for the change
+AD4- to 32-bits with 8 bits for a character, although there was also much
+AD4- ballyhoo about 32 being a power of 2 whereas 36 was not.
+AD4- 
+AD4- In any case, 32 bits carried the day.  Are there any general purpose
+AD4- machines today with other than 32-bit (or a multiple thereof) words?
+AD4- 
+AD4- Cheers, Wes 


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