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Re: Harvest time!

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Lynn Wheeler <lynn@garlic.com> posted: 
> Amdahl won the battle to make ACS, 360 compatible ... and he left when
> it was killed (folklore that they were afraid ACS/360 would advance the
> state of art too fast and IBM woould loose control of the market).
> https://people.computing.clemson.edu/~mark/acs_end.html

That acs_end.html file, discussing designs of the late 1960's
contains many lines like
> the current ACS design needs 7 levels of logic per stage,
> thus 12.5 nsec cycle time ...

This confuses me.  The 370/168 -- dominant until the 3033 in the late 1970's
-- had 80 nsec "cycle time", and logic gate delays
were about 2 nsec minimum even without considering line delays or anything
more complicated than OR or NOR.  Even the mini-"cycles" on the 370/135
were 55 nsec IIRC.  What are these super-short "cycle times" repeated
throughout that document?

I consulted for NatSemi in 1980; they had purchased Exsysco, which had
built a 370/158 "lookalike," and was then attempting a 3033 lookalike.
Two interesting anecdotes about these machines:

(1) Exsysco's "AS" (158 lookalike) machines came in two models,
one significantly faster (and more expensive) than the other.
An anecdote repeated so often that I assume it was true was that the
slow machine could be converted into the faster machine by adding
(or removing) a single wire!  Supposedly some of the NatSemi/Exsysco
FE's went into business removing that wire for customers!

(2) The 3033 lookalike was never completed:  A prototype was built but it
never ran at the 3033 57-nsec cycle time, and no slower speed was
acceptable.  I was consulting for a different project, but the 3033-
lookalike director wanted to hire me when that small project was complete.
Stupidly I began looking at their 3033-lookalike without a contract
and delivered a preliminary report.  Exsysco used much larger
circuit boards than IBM and I wondered if this "failure to take
advantage of the 3rd dimension" imposed a speed penalty.  Already
pessimistic, management canceled the whole project upon that
(uncompensated!) report.

I think IBM sought to make things difficult for these "lookalike"
competitors.  As just one example, consider the SE instructions
(E5 opcode?) introduced in 1978.  ALL previous instructions had
B+ddd as the meaning of the 2nd or 3rd halfword in an instruction.
Did IBM deviate (unnecessarily) from this in hope of making life
difficult for firms that were doing the B+ddd automatically?

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Harvest time! David Lesher <wb8foz@panix.com> - 2026-10-01 02:06 +0000
  Re: Harvest time! Anton Antimo <anton@safunu.org> - 2026-10-01 11:26 -0300
    Re: Harvest time! Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-10-01 23:44 +0800
    Re: Harvest time! David LaRue <huey.dll@tampabay.rr.com> - 2026-10-01 21:22 +0000
  Re: Harvest time! Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-01 22:11 +0000
    Re: Harvest time! Lars Poulsen <lars@beagle-ears.com> - 2026-10-01 20:05 -0700
      Re: Harvest time! Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-02 04:50 +0000
        Re: Harvest time! Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2026-10-02 18:17 +0000
          Re: Harvest time! Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-02 21:44 +0000
            Re: Harvest time! Lynn Wheeler <lynn@garlic.com> - 2026-10-02 13:43 -1000
              Re: Harvest time! James Dow Allen <user4353@newsgrouper.org.invalid> - 2026-10-03 19:31 +0000
                Re: Harvest time! Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-03 21:43 +0000
                Re: Harvest time! Lynn Wheeler <lynn@garlic.com> - 2026-10-03 16:16 -1000
                Re: Harvest time! James Dow Allen <user4353@newsgrouper.org.invalid> - 2026-10-06 21:23 +0000
  Re: Harvest time! John Levine <johnl@taugh.com> - 2026-10-02 01:48 +0000

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