[TUHS] Can PDP-11/23 PLUS run Unix?

[Clem Cole via TUHS]

below..

On Fri, Feb 27, 2026 at 4:48 PM Noel Chiappa via TUHS <tuhs at tuhs.org> wrote:

>  Why all the attention to instruction backup, if it was already done?
>
I have no idea. And sadly, we can not ask him.  We lost him several years
ago to cancer.   I tried to get Lisa (his widow) to let me review his
collection of technology, but she wouldn't allow it, and I believe some
treasures have been lost.  I know he had some stuff from CMU (such as his
ISPS system, which he developed for his PhD).

>
> Also (unrelated to the above, but since I'm posting) use of overlays in the
> kernel, useful on machines without separate I+D, came in with BSD 2.9:
>
Actually, it came from v7m.  Fred Cantor wrote it.  Bostic and the 2. X
crew pulled it from v7m.

v7m and 2.XBSD can run on both Unibus and QBUS PDP-11s, but as I said, the
F-11 lacks a separate I/D Space and does not support supervisor mode (only
user and kernel), so 2.11BSD will not work.

It's a matter of taste and effort between Ultrix-11 and 2.9BSD.  If you
have a Unibone or a Qbone, thern its easy to use simh to create the proper
disk images.   Then load them into the SSD on the Unibone/QBone.   A while
back, I helped Dave Plummer with getting his PDP-11/83 running with 2.11BSD
using this scheme.

Clem