UNIX/VENIX on PDP-11 (was Re: VENIX on Rainbow)

[Ethan Dicks]

On Thu, Jun 20, 2019 at 9:57 AM Eric Christopherson
<echristopherson at gmail.com> wrote:
> On Wed, Jun 19, 2019 at 9:09 PM Ethan Dicks via cctalk <cctalk at classiccmp.org> wrote:
>> On Wed, Jun 19, 2019 at 8:47 PM Cameron Kaiser via cctalk
>> <cctalk at classiccmp.org> wrote:
>> > > Interesting.  I have VENIX on a Professional 350 (it was one of the
>> > > machines I had on display for VCF East).  I haven't tried fiddling
>> > > with VENIX on a Rainbow, though I did know it existed.
>> >
>> > Venix/PRO on a 380 here. I like it. Thinking about ways to make it
>> > primitively networked.
>
> I'm really glad to see this discussion; I have a PDP-11/23+ waiting to be poked at, but didn't know about the Professional at all; it's interesting to see that Venix can run on the /23+ as well.

Venix/Pro has a driver for the Pro RD50 disk controller.  This is not
an MSCP controller, it's its own thing and fairly low-level (the
driver has to know details about how drives work, not a pile of data
blocks).  One could probably write an MSCP driver for a Qbus machine
but you'd probably want a source kit to get the Venix side of things.

There _are_ versions of UNIX that will run on the 11/23.  Your biggest
challenge is using nothing newer than 2.9BSD (because the KDF11 lacks
Split I&D) and finding a combination of disk controllers and OS
support that match up (there are patches for 2.9BSD that back-port an
MSCP driver for the RQDX3 but I haven't personally played with them -
my 2.9BSD work was on Unibus, on an 11/24 with either RL11/RL02 or
RK611/RK07 drives).

If you have an RLV11 or RLV12 and 1-2 RL02 drives, that's a good
starting point for UNIX on an 11/23.  If all you have for disk is
something on an RQDX3, you might be limited to patched 2.9BSD.

> Whether it's a good choice of OS (compared to, say, 2.9BSD) or not I don't know.

The version on my machine (Venix/PRO v1) is largely a port of UNIX v7.
I think Venix/PRO v2 for the Pro 380 is something different (and
newer) under the hood, to support Split I&D for example.  Not sure
about MSCP or network drivers there though.

It was definitely interesting writing code on my Venix box at VCF East
- turns out it has a minor Y2K problem.  Internal date representation
is seconds-since-the-epoch, of course, but the date command itself
only allows 2-digit year.  You can set the time to 23:59:00 31-Dec-99
and let it roll over then repeat each year until you get to the
current one... which could be done by a shell script, of course, or,
what I did was to write a simple program to accept the current time in
seconds and feed that to stime.  Nearly all my experience is with
later (post-1984) versions of UNIX so I had a bit of learning to do
(or is that learning to forget?) to get things working there but I
did.  I wish I'd packed my 1975 pocket flip-guide, but at least I had
all the original paper Venix/Pro docs (also up on Bitsavers).

-ethan

-ethan