On Mon, Nov 20, 2017 at 11:03 AM, ron minnich <rminnich@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.