[TUHS] UNIX on S/370

Clem Cole clemc at ccc.com
Tue Nov 21 02:31:40 AEST 2017

On Mon, Nov 20, 2017 at 11:03 AM, ron minnich <rminnich at gmail.com> wrote:

> When would this  have been? In 1978 Szurkowski and I went to the
> then-famed Atlantic City Computer Show (still in Atlantic-city, pre-casino,
> so it was cheap, and very much the place Springsteen wrote about) and
> stopped at Princeton and talked to someone who was doing such a port. Would
> that have been Tom?
​I would think so.​

> I stopped at the now-closed Palo Alto office of IBM in 1991 or so. Some
> ex-Locus researchers told me that the 'move to native' for AIX was being
> slowed down a bit by the lack of people who knew how channels really worked
> ... they implied that many of them had retired! Does any of that comment
> ring true?
​I can not say.  I'm sure who that would have been.​  The Locus AIX/370 was
mostly in LA [lead by Bruce Walker and late Gerry Popek].

IMO: The issue was less understanding how channels worked, as much as the
biasing between the UNIX I/O model *vs.* the mainframe I/O model.   360 and
CDC boxes for that matter, were a coprocessor that was programmed for the
I/O.   Figuring out how to splice that into the UNIX world efficiently was
not always easy.

I fought this war many times over my career.   Often it was just easier to
have a lot of really fast similar processors in the main CPU.   The idea
being that if you have enough of them and anyone will do, you don't have to
think about it/do anything special in the SW.

In the the case of the IBM channel or the CDC PPUs, or even later the
Masscomp machines, if you have these coprocessors that can do a lot of the
work for you, but are not as fast as or as flexible as the main processor,
what is best to process what part of the I/O where?

In the case of the MC500 the network processor was a 186 then a 286, and we
ran the TCP stack on it so the host would not have to do anything.   By the
time of the MC5000, we just ran the 286 as a very large packet buffer but
could smooth out packet or interrupt storms, which was the same trick we
did on the CDC Cyber years earlier (the PPU  had monitored the network link
the same way).

I believe that AIX/370 struggled with some of those same choices.
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