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From: "Stephen Fuld" <SFuld@alumni.cmu.edu.invalid>
Newsgroups: comp.arch
Subject: Re: backward architecture, The Design of Design
Date: Fri, 10 May 2024 06:20:00 -0000 (UTC)
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Tim Rentsch wrote:

> "Stephen Fuld" <SFuld@alumni.cmu.edu.invalid> writes:
> 
> > The key innovation that IBM made with the S/360 was to announce
> > systems with a wide range of performance *at the same time*,
> > i.e. different Y values and the same X value.
> 
> I would argue that this property is only one of three factors
> that made System/360 successful, and perhaps the least important
> of the three.  The other two factors are, one, addressing both
> business computing and scientific computing rather than having
> separate models for the two markets, and two, replacing and
> discontinuing all of IBM's other lines of computers.  I think
> it's hard to overstate the importance of the last item.

I didn't mean to imply that the performance range was the only factor
in S/360's success.  Just that with S/360, IBM was the first to use
that strategy, and it was a factor in its success.

As to the other two factors you mentioned, I don't necessarily
disagree, but I do want to note that discontinuing older lines of
computers was factiltated by the ability of various S/360 models to
emulate various older computers.  So a site that had, say a 1401, could
upgrade to a S/360 mod 30, which could run in 1401 emulation mode, so
sites could keep their old programs running until they were replaced by
newer nativve S/360 applications.  Similarly for 7080 emulation on
s60/65s.  There were probably others that I don't know about.

And, of course, we have already discussed several other factors in its
success.





-- 
 - Stephen Fuld 
(e-mail address disguised to prevent spam)