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From: pdb@sei.cmu.edu (Patrick Barron)
Newsgroups: comp.sys.dec
Subject: Re: UNIX on a PDP11
Message-ID: <754@aw.sei.cmu.edu.sei.cmu.edu>
Date: Thu, 19-Mar-87 19:07:00 EST
Article-I.D.: aw.754
Posted: Thu Mar 19 19:07:00 1987
Date-Received: Sat, 21-Mar-87 07:24:51 EST
References: <1741@a.cs.okstate.edu> <3335@ihlpa.ATT.COM>
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Reply-To: pdb@sei.cmu.edu.UUCP (Pat Barron)
Organization: Carnegie-Mellon University, SEI, Pgh, Pa
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In article <3335@ihlpa.ATT.COM> normt@ihlpa.ATT.COM (N. R Tiedemann) writes:
>....
>could stay the same, but I doubt it. The 11/40 is a vintage PDP (ie Unibus), it
>has very little capability for virtual memory, only an 18 bit address bus, and
>the only ones that I know are still around, are in my old lab at the U of Wis.
>in Madison, and in the Digital Museum. The 11/34 was (about 1978) the newest
>and best Q-bus machine, it does support virtual memory, and will easily run a
>multitasking operating system (11/40 will only run RT-11 without a lot of
>overhauling). 

Sorry, but the 11/34 is a Unibus machine too, and also only has an 18-bit
address bus.  The 11/34 doesn't outperform the 11/40 except for floating
point (where it clearly wins), unless you have an 11/34C, which pretty much
blows the 11/40 away (the 34C has a fast cache, the 40 doesn't have any
cache).

No PDP-11 supports "virtual memory" (at least not the way most of us think
of it), but the 11/40 supports the same memory management that the 11/34
does.

As long as you have EIS and memory management, you can run just about any
operating system you want on it.  I've run 2.9BSD, DEC V7m Unix, and RSX
on an 11/40 with no real problems.

The Q-Bus 11's are the LSI-11 (a/k/a PDP-11/03), 11/2, 11/23, 11/53, 11/73,
and 11/83.

--Pat.