[TUHS] PDP-11 questions

Norman Wilson norman at oclsc.org
Mon Jan 25 08:40:41 AEST 2016

Noel Chiappa:

  I'd lay good money that the vast majority of PDP-11's never ran Unix. And
  UNIX might have happened on some other machine - it's not crucially tied to
  the PDP-11 - in fact, the ease with which it could be used on other machines
  was a huge part of its eventual success.


I have to disagree in part: the PDP-11 is a big part of
what made UNIX so widespread, especially in university
departments, in the latter part of the 1970s.

That wasn't due so much to the PDP-11's technical details
as to its pricing.  The PDP-11 was a big sales success
because it was such a powerful machine, with a price that
individual departments could afford.  Without a platform
like that, I don't think UNIX would have spread nearly the
way it did, even before it began to appear in a significant
way on other architectures.  Save for the VAX, which was
really a PDP-11 in a gorilla suit, that didn't really happen
until the early 1980s anyway, and I'm not convinced it
would have happened had UNIX not already spread so much
on the PDP-11.

It worked both ways, of course.  I too suspect that a
majority (though I'm not so sure about `vast') of PDP-11s
never ran UNIX.  But I also suspect that a vast majority
of those that did might not have been purchased without
UNIX as a magnet.  I don't think those who weren't
around in the latter 1970s and early 1980s can appreciate
the ways in which UNIX captured many programmers and
sysadmins (the two were not so distinct back then!) as
no other competing system could.  It felt enormously
more efficient and more pleasant to work on and with
UNIX than with any of the competition, whether from DEC
or elsewhere.  At the very least, none of the other
system vendors had anything to match UNIX; and by the
same token, had UNIX not been there, other hardware
vendors' systems would have had better sales.

Sometime around 1981, the university department I worked
at, which already had a VAX-11/780 and a PDP-11/45 running
UNIX, wanted to get another system.  Data General tried
very hard to convince us to buy their VAX-competitor.
I remember our visiting their local office to run some
FORTRAN benchmarks.  The code needed some tweaking to
work under their OS, which DG claimed was better than
UNIX.  Us UNIX people had trouble restraining our chuckles
as we watched the DG guys, who I truly believe were experts
in their own OS, taking 15 or 20 minutes to do things that
would have taken two or three with a few shell loops and
ed commands.

DG did not get the sale.  We bought a second-hand VAX.
Blame UNIX.

Norman Wilson
Toronto ON

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