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From: rdp@teddy.UUCP (Richard D. Pierce)
Newsgroups: comp.sys.dec
Subject: Re: UNIX on a PDP11
Message-ID: <3864@teddy.UUCP>
Date: Thu, 19-Mar-87 13:54:49 EST
Article-I.D.: teddy.3864
Posted: Thu Mar 19 13:54:49 1987
Date-Received: Sat, 21-Mar-87 06:01:32 EST
References: <1741@a.cs.okstate.edu> <3335@ihlpa.ATT.COM>
Reply-To: rdp@teddy.UUCP (Richard D. Pierce)
Organization: GenRad, Inc., Concord, Mass.
Lines: 53

In article <3335@ihlpa.ATT.COM> normt@ihlpa.ATT.COM (N. R Tiedemann) made
several erroneous statements in reply to some questions Chris Shuermann
had about 11/34's:
->>
->> I have recently acquired 2 PDP11/34s.
->> Now, I am in need of some info. From what I can tell, they have
->> been upgraded to 11/40s. Is this even possible?? All the drawings
->> are for an 11/40.  I have several RK05j HDs (well, they work :-)
->> I have no docs at all on the OS (which I am reasonably certain is RSX )
->> By now I am sure you can tell that I live in the UN*X world.
->> the RK05s or will I have to get something larger. Again an assumption:
->> RK05s are 5Meg ?????
->> Chris Schuermann
->
->To upgrade an 11/34 to an 11/40 would be a step back in time, 

This is certainly true, the 11/40 predates the 11/34 by about 6 years, but ...

->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). 
->

The PDP-11/34 is a UNIBUS machine as well, it also support 18 bit addressing,
and it has the same memeory management scheme as the 11/40 (that is, if the
11/40 even had 18 bit addressing at all, which I don't quite remember).

PDP-11/40's routinely ran DOS-11 (in the VERY early days) RT-11, RSTS/E,
RSX-11D, RSX-11M, RSX-11S and others, just like an 11/34!

->The RK05's are 2.5Mbyte drives, (I don't know what the j means), to run a
->modern version of Un*x it would take a couple of these. The RK05 and RK06
->are the only drives that still support the PDP8 family. (At least that's
->what I can find in the DEC catalog.)
->

RK05J's are 2.5 megabyte removable packs, as aooposed tt RK05F's, which are
fixed 5 megabytes that appear as two logical 2.5 megabyte drives (the major
difference is the lack of the door lock mechanism in the F's and slightly
different track seeking logic.

->So in summary, if they are 11/34's you could run a Un*x, on them. I have
->seen Un*x for Q-bus machines, the only problem may be distribution. If
->it really is an 11/40 (Unibus) you may have real problems running a "big"
->operating system on it. Most software that specs for UNIBUS requires
->an 11/70 with its expanded memory capabilities.
->

Dick Pierce