PDP 11 Victory!

[Ethan Dicks]

On Mon, 14 Feb 2005 10:01:19 -0500, Paul Koning <pkoning at equallogic.com> wrote:
>  Vintage> Getting NetBSD onto it would be cool.
> 
> NetBSD?  I don't think that has a PDP11 port. 

I would agree with that suspicion.

> Did any of the 2.x BSDs work on 18 bit PDP11s?  Or PDP11s without
> supervisor mode?  I always thought that one or the other was required,
> but I may be confused with Bell Labs Unix.

I have run 2.9BSD on an 11/24 w/two RL02 and 1MB of RAM.  Besides enough memory,
the big limitation with PDP-11 UNIX is if the processor supports
"Split I&D Space" (for
the PDP-11 novices, it's the ability to have the 16-bits of
"Instruction Space" (code) and
the 16-bits of your "Data Space" (data) in different regions of
physical memory.  It allows
one to have a single program access up to 128K without tweaking the MMU a second
time.  So on an 11/34 or 11/24, one can only have 64K that contain
both a program's
code and its data (meaning large programs _must_ use overlays).  I
forget when 2BSD
started requiring Split I&D, but it was either 2.10 or 2.11 (and 2.11
supports MSCP out
of the box).

I have not run 2.9BSD on an 11/34, but if the kernel is small enough,
it may be possible.
Newer versions would not be.

-ethan