Re: The Design of Design

John Levine wrote:

According to Stephen Fuld <SFuld@alumni.cmu.edu.invalid>:

Thomas Koenig wrote:
 

John Levine <johnl@taugh.com> schrieb:
 

They had the insight to see that the 16 fixed sizs registers

could >> > be in fast storage on high end machines, main memory on
low end >> > machines, so the high end machines were fast and the low
end no >> > slower than a memory-memory architecture which is what it
in >> > practice was. It was really an amazing design, no wonder it's
the >> > only architecture of its era that still has hardware

implementations.

 
Yes, although it isn't clear how much of its success is due to
technical superiority versus marketing superiority.

 
S/360 invented eight bit byte addressed memory with larger power of 2
data sizes, which I think all by itself is enough to explain why it
survived.

Of cpurse, I agree about IBM inventing the 8 bit byte (although the
Burroughs large scale systems used it too), and the power of two data
sizes (although the Univac 1108 and successots sort of had that with
quarter word, half word word and doube word data sizes).  While
important, I am not sure about succfient.

I do want to note that another factor in S/360's success was the
quality of the paper peripherals, expecially the 1401 printer, which
was a true marvel in its time.  IBM got that advantage from their long
experience with punch card business systems.




 All the others, which were word or maybe decimal digit

addressed, died. Its addresses could handle 16MB which without too
many contortions was expanded to 2GB, a lot more than any other design
of the era. We all know that the thing that kills architectures is
running out of address space.

The Univac 1110 (circa 1972), (about a devcade before XA) had banking,
which allowed an instruction to address anywhere within a 262K
(approximately 1 MB) "window" into what could be an "address space" of
about 4 GB.  It was a little awkward in that, while you could have 4 of
such "windows" available at any time, changing windows required
executing an, (unprivlidged) instruction.





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