PDP-11/05 returns to life
ethan.dicks at gmail.com
Tue Jan 6 15:37:45 CST 2009
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
> ... 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
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
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.
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