PDP-11 Xenix (LONG)

Frank Wortner fwortner at prodigy.net
Sat Oct 11 00:57:18 AEST 1997

Since I'm the one that started this --- albeit indirectly --- let me try to

Way back when --- about 1981 or 82 --- I worked for a small (now defunct)
software company.  We owned 2 PDP-11/23s.  Initially,  we ran a distribution
of the Sixth Edition on them.  That came from a company in New York ---
that's where I am geographically,  BTW --- called Yourdon.  The system was
called UV6.

After a while,  we decided to upgrade to V7.  At the time,  we had begun a
relationship with another (now defunct) firm called Lifeboat Associates
(also in New York,  later in Tarrytown, NY).  They distributed microcomputer
software,  principally CP/M-based.  They were a Microsoft distributor.
Microsoft had just started Unix development at the time.  Lifeboat sold us a
V7 system:  Microsoft PDP-11 Xenix.  I know it was Microsoft because the
tape lables said so, and I remember that the line printer printed release
notes contained a banner page that indicated that they came from Microsoft's
DEC 20(!) (cheerfully named "Microsoft Heating Plant").

PD.-11 Xenix was essentially V7,  but it had a few added features.
Processor support included all models of PDP-11 with MMUs:  23s, 34s, 40s,
45s, 55s, 60s, and 70s.  It had split I&D space emulation --- borrowed,  I
believe from 2.something BSD.  That emulation required a grand total of
three(!) link passes,  but the compiler driver was modified to do this
automatically if you specified the "-j" option.  Instead of source,  the
kernel was delivered mostly as .o files and .a libraries,  so you could
reconfigure the OS without source.  The reconfigure programs just spat out
some assembly language and C "glue" that you compiled and linked with the .o
and .a files.  In fact,  this was pretty much automated.  The system also
had a rather extensive /etc./shutdown shell script which calmly and
thoroughly brought the system to a quiescent state and could optionally
reboot or halt it.  Although the OS was pretty big --- I find it amazing
that I thought of it as "big" ;-) --- you could,  with some effort build a
boot floppy on a RX02 diskette.  That could run exactly 1 (one) process ---
the RX02 system had *no* swap space.   I remember system recovery sessions
in which I constantly had to boot the floppy,  see the shell prompt,  and
then "exec fsck" and watch as fsck finished its run,  and init respawned the

Anyhow,  I know I *used to have* the release notes and I *might* have had
the tape,  but both,  sadly,  are probably lost.  I was wondering if anyone
else might have seen or,  even better,  still has a tape of this rare
version of V7.  Perhaps there's an archive at Microsoft or SCO that harbors
a tape.  Most software firms do have some sort of policy about placing
products in escrow with a third party.  Maybe this still exists.  If not,
that's OK.  If SCO is kind enough to allow source licensing to individuals
for noncommercial use,  then this largely becomes a moot issue.

Full source V7 (or even better 2BSD) is probably a more "interesting" system
from a hobbyist or preservationist point of view,  particularly if you're
like me and don't have or care to own actual PDP-11 hardware.  I'm quite
happy to run John Wilson's and Bob Supnick's wonderful emulator programs
with whatever software I can obtain.  They let me have the PDP-11 models I
worked on (23, 34, 45) as well as those I'd like to have had (70) without
the hassle and expense of maintaining the actual hardware.

BTW,  if John or Bob reads this list,  l'd like to say "Thank you" to both
of them.  Also thanks to Warren for his work preserving the old Unix
software.  It's a great deal of fun to see old "friends" again,  and I think
it will be just as much fun to see software and "hardware" combinations that
I didn't have access to in the "good old days."  Thanks also to SCO for
binary licenses for these "historic" systems;  I hope that they will be able
to license source code in the near future.

Sorry for the long ramble and thanks for reading!


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