VAXen and minimal memory (was Re: The PDP11/04 has landed..)

Guy Sotomayor ggs at
Thu Feb 11 14:52:22 CST 2016

> On Feb 11, 2016, at 12:39 PM, William Donzelli <wdonzelli at> wrote:
>> Indeed.  RSTS/E did better, with less hardware -- 64 users on an 11/70 was no problem, and earlier on you could run 16 users on an 11/20 (though not all that comfortably).
> It all depends on what the users are doing, of course. When I went to
> school back in the late 1980s, the main computer was (for a while) a
> VAX-11/780. Things started to get dodgy with 30 engineering students
> online compiling and running crap code, and almost useless when 35
> were on.
> There was also an ancient PDP-11/70 that ran some variant of Unix, and
> that general became useless after about 10 students were online.

In the mid-to-late 70’s, I was an undergrad at CMU.  I had accounts on the
CS department’s systems.  When I started, it was 2 KA10s.  Eventually a
KL10 was added (all running a *heavily* patched version of TOPS10).

During the day it was nearly impossible to get stuff done with ~200 faculty
and grad students on-line (on each system).

I also spent a fair amount of time on C.MMP but I only wrote code for it and
never actually did any “production” work on it (but it was *cool* to see…cross
point switch was the ultimate in blinking lights!).

TTFN - Guy

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