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

Paul Koning paulkoning at
Thu Feb 11 15:50:42 CST 2016

> On Feb 11, 2016, at 3:52 PM, Guy Sotomayor <ggs at> wrote:
>> ...
> 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).

The most amazing timesharing system I've seen is PLATO.  In 1977: 600 active users, highly interactive, on a pair of Cyber 73 (CDC 6500) dual CPU machines.  Each CPU good for about 1-2 MIPS, so that's pretty good.  Even with a customized workload, that was a tough lift; typically about half the keystrokes would require "real work".  Not like a command line based system where most keystrokes just get echoed and stuffed into the current line buffer.


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