Re: [TUHS] First Unix that could run on a PDP-11 with QBUS - TUHS

27 Jul 2014

...
  From: Mark Longridge &lt;cubexyz(a)gmail.com&gt; 
...
  I was digging around trying to figure out which Unixes
would run on a
 PDP-11 with QBUS. It seems that the very early stuff like v5 was
 strictly UNIBUS and that the first version of Unix that supported QBUS
 was v7m (please correct me if this is wrong). 
That may or may not be true; let me explain. The 11/23 is almost
indistinguishable, in programming terms, from an 11/40. There is only one
very minor difference (which UNIX would care about) that I know of - the
11/23 does not have a hardware switch register.

Yes, UNIBUS devices can't be plugged into a QBUS, and vice versa, _but_ i)
there a programming-compatible QBUS versions of many UNIBUS devices, and ii)
there were UNIBUS-QBUS converters which actually allowed a QBUS processor to
have UNIBUS peripherals.

So I don't know which version of Unix was the first run on an 11/23 - but it
could have been almost any.

It is quite possible to run V6 on an 11/23, provided you make a very small
number of very minor changes, to avoid use of the CSWR. I have done this, and
run V6 on a simulated 11/23 (I have a short note explaining what one needs to
do, if anyone is interested.) Admittedly, this is not the same as running it
on a real 11/23, but I see no resons the latter would not be doable.

I had started in on the work needed to get V6 running on a real 11/23, which
was the (likely) need to load Unix into the machine over a serial line. WKT
has done this for V7:

  http://www.tuhs.org/Archive/PDP-11/Tools/Tapes/Vtserver/

but it needs a little tweaking for V6; I was about to start in on that.

...
  I have hopes to eventually run a Unix on real hardware

As do a lot of us... :-)

...
  It seems like DEC just didn't make a desktop that
could run Bell Labs
 Unix, e.g. we can't just grab a DEC Pro-350 and stick Unix v7 on it. 
I'm not sure about that; I'd have to check into the Pro-350. If it has memory
mapping, it should not be hard.

Also, even if it doesn't have memory mapping, there was a Mini-Unix done for
PDP-11's without memory mapping; I can dig up some URLs if you're interested.
The feeling is, I gather, very similar.

...
  it would be nice to eventually run a Unix with all the
source code at
 hand on a real machine. 
Having done that 'back in the day', I can assure you that it doesn't feel
that different from the simulated experience (except that the latter are
noticeably faster :-).

In fact, even if/when I do have a real 11, I'll probably still mostly use the
simulator, for a variety of reasons; e.g. the ability to edit source with a
nice modern editor, etc, etc is just too nice to pass up! :-)

	Noel