Re: backward architecture, The Design of Design

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)