PDP-11/05 returns to life

Ian King IanK at vulcan.com
Tue Jan 6 16:17:34 CST 2009

If you google the terms, I recall a school website that had a sample circuit for converting between RS232 and 20mA.  There are also gadgets you can buy to do it - again, Google is your friend.  -- Ian

-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Tobias Russell
Sent: Tuesday, January 06, 2009 2:10 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: PDP-11/05 returns to life

Excellent so all this sounds encouraging. I've had a look at the Farnell
website and there seems to be plenty of choice of 110V 12cm fans so
buying some replacements shouldn't be a problem.

With the onboard console, how hard is it to build a device to convert
current loop into RS232 levels?

It appears I have a PDP-11/05-JA backplane so I should be able to get my
RX11 into slot 1. The next challenge will be to get an RX01 disk built
with RT11 on it. I'm planning on making the image with SIMH and then use
vtserver to copy the image onto the RX01 (connected to my 11/73). Does
this sound like a sane approach?


On Tue, 2009-01-06 at 16:37 -0500, Ethan Dicks wrote:
> On Tue, Jan 6, 2009 at 3:19 PM, Tobias Russell <toby at coreware.co.uk> wrote:
> > I managed to coax my PDP-11/05 back into life today and ran a few simple
> > programs on it successfully.
> >
> > As a result a few questions for the experts out there:
> >
> > 1. To get it up and running I had to replace its two fans both of which
> > had failed which I did by scavenging another 11/05 chassis I have.
> >
> > Does anyone have any tips on reviving failed fans?
> Just what you've done... clean and lube (WD-40 is *not* lubricant!)
> If they really won't spin and they are oddball fans, you might need
> exact replacements (ISTR the 11/40 or 11/45 has that problem), but if
> you find a modern fan that's the same size and voltage, you are
> probably OK.
> > ... if recovery is impossible can anyone suggest suitable replacements? The
> > current ones are labelled Super-Boxers
> I think you might still be able to get fans like that, but I haven't
> tried in at least 5 years.
> > 2. Is there a chasing lights program I can run on the 11/05? Would be
> > nice to see it visibly doing something
> From: <http://www.psych.usyd.edu.au/pdp-11/11_40.html>
> Toggle in the following program and start at 001000. Note that the RUN
> light will go out!
>       Location        Contents        Opcode          Comment
>       001000          012700          mov #1,r0       Load 1 into R0
>       001002          000001
>       001004          006100          rol r0          Rotate R0 left
>       001006          000005          reset           Initialise bus (70ms)
>       001010          000775          br .-4          Loop back to 'rol r0'
> I do not know if this will work on an 11/05 because of the 'reset'
> instruction, but it's a start.  You could replace the reset
> instruction with an inner loop on r1 without too much difficulty if
> this won't work on your machine.
> > 3. At the moment the machine has 16KW of core (2 x 8KW planes). This
> > together with the CPU fills all but the last slot on the Unibus (its a
> > 5inch box so only 9 slots). I'd like to fit a DL11 so that I have some
> > serial comms and ideally an RX11 as well so I can hook up my RX01 drives
> > and boot RT-11. Can I make use of the 9th slot or does this have a
> > special purpose? There is a lot of wire wrap going to slot 9 so I'm
> > guessing its not suitable.
> My memory is that you can use the 9th slot for an SPC (small
> peripheral controller), but check the 11/05 handbook to be certain.
> IIRC, The RX11 and DL11 do not need NPR (but the RX211 might), but
> look those up in a mid-1970s handbook to be certain.
> > 4. What versions of RT-11 is suitable for an 11/05 and what is the
> > minimum memory to run it?
> I would think that RT-11 v4.0 would work nicely on an 11/05.  I'm
> pretty sure even the newer stuff will work, but since you don't care
> about MSCP support or other modern niceties, it may not be a big win
> for you.  Games and such, at least the ones I know of, should run on
> V4 and V5, as long as you have enough core for the app itself.  Don't
> expect to run ADVENT without a full boat of memory, but there are
> plenty of smaller apps out there.
> -ethan

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