🚀 go-pugleaf

On Friday, March 30, 2018 at 10:29:39 PM UTC-4, Lynn Wheeler wrote:
> hancock4@ writes:
> > From what I've read, creating a compatible product line across
> > all four modes* in 1960 would require a lot of compromises that
> > would downgrade performance and increase cost.  In 1960, computer
> > hardware was still extremely expensive, not that fast, so including
> > circuits to do unwanted functions was an unnecessary expense.  Indeed,
> > even in the early days of S/360 and even PC's, floating point was an
> > optional feature.  The addressing needs on a small machine are different
> > than a large machine; S/360 base+displacement was a compromise.
> 
> re:
> http://www.garlic.com/~lynn/2018c.html#15 Old word processors
> http://www.garlic.com/~lynn/2018c.html#16 Old word processors
> 
> claim was that in that emerging computing market, compatibility
> outweighed model performance advantage.
> 
> majority of 360s were microprogrammed ... so it wasn't all those
> circuits.

I dare say that if the S/360-30 did not have to be compatible,
it probably could've been a lot cheaper, even with micro-code.

I don't know the innards or functionality of a 1410, but 
according to the bitsavers manuals, it had a lot of extra
features that were optional or not even available on the 1401.
I'm only guessing, but I suspect a 1410 built with SLT chips
would've been quite a machine with excellent performance/cost
and quite popular.

Note that even in the "compatible" S/360 line, they built certain
model 2x that were not fully compatible in order to keep the
price down.  More significantly, the System/3 line and successors,
had to be built with a totally separate incompatible architecture
in order to keep their price down, and that was in 1970.

On the other end of the line, I don't believe today's IBM
super computers are compatible with the S/360 (Z series).
I'm guessing those who seek supercomputers are not planning
to run their payroll or general ledger on them.

Actually, I do wonder what percentage of S/360 customers did
_both_ business and science/engineering programming on their
machines.  I think colleges did a lot of this--the researchers
shared the machine with the business office.  But how common
was it for some modest sized business, with their model 30
or model 40, doing some Fortran alongside their payroll?
It just seemed to me that companies that were doing heavy-duty
research that needed a computer got a PDP dedicated to lab
work; some got an 1130.  (Obviously there were some organizations
that did both, but how many?)





> don't know much about 360 microprogramming ... a little more about
> 115-II/125-II and 138/148. they avg. 10 native instructions for every
> (simulated 370).

This bitsavers document gives a good introduction:
http://www.bitsavers.org/pdf/ibm/370/GF20-0385-0_An_Introduction_to_Microprogramming_Dec71.pdf


[snip]