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PDP-11/40 Project at the RICM

m_thompson

m_thompson

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We just started a PDP-11/40 project at the RICM. We got the system from Fairfield University who got it from yale University. Yale gutted the system and installed a hex-wide Q-bus backplane, 11/23 CPU, Memory, 4x Serial Ports, and GPIO cards. They even made a wire-wrap board to interface to the 11/23 CPU.

We need to repair a cooked connector on the power supply harness and on the power distribution backplane that feeds the first SLUs. We have two giant Unibus expansion chassis that we can use for parts to fix this chassis. We also need to add another +5 power supply when we populate the last slots in the chassis.

We have two complete sets of PDP-11/35 - PDP-11/40 CPU boards, backplanes, memory, serial ports, consoles, VT11, RL11, RX11, clocks, GPIO and other Unibus boards to go in this chassis.

We plan to set the system up to run all of the DEC operating systems by swapping RL02 packs, and to try running UNIX.

If we run into unsolvable road blocks with the 11/40 we have two PDP-11/45 systems that we could use to make a running 11/45. We even have a PDP-11/70, but no spares for it.
 
The only problems you might have running something like V7 is finding the required option boards for the CPU
You're going to need the line clock and KM11 if you're going to run RSX-11M. I forget if Unix needed EIS
My very first exposure to Unix was when someone put a system together from parts in the 70s to run V7.
 
Snap a picture of the Q bus "interface", I'm kind of curious if it is one of those Plessey backplanes.

Was the original 11/40 backplane retained?
 
czunit said:
Snap a picture of the Q bus "interface", I'm kind of curious if it is one of those Plessey backplanes.

Was the original 11/40 backplane retained?
Click to expand...
Information on the modified machine is here:

Everything from the original 11/40 CPU, Memory, and I/O was removed by Yale.
The current idea is to run 2.9BSD UNIX.
We have a KJ-11 stack limit board, so we should be able to run RSX.
 
Hm, that is not a DEC backplane, looks professional/designed by a real company. More interesting I don't see a +15 to +12 voltage converter to run the Q Bus stuff. Was it using the 11/40 power supplies (which I thought put out +20, -15, +15, +5 and such)

I have a Plessey backplane that would go into a BA11 and allow one to run a Q bus system. It would then attach to the Unibus goodies with a Plessey Quniverter. 18 bit only but more than enough to replace an 11/34.
 
And with the stack limit option (a simple "single width" board), you probably need the MMU as well.
Note that the 11/40 requires jumpers on several boards to be wrapped correctly when adding options to the CPU.
IIRC, for the KW11 (line time clock) you even need to do some work on the 11/40 backplane!
 
czunit said:
Hm, that is not a DEC backplane, looks professional/designed by a real company. More interesting I don't see a +15 to +12 voltage converter to run the Q Bus stuff. Was it using the 11/40 power supplies (which I thought put out +20, -15, +15, +5 and such)

I have a Plessey backplane that would go into a BA11 and allow one to run a Q bus system. It would then attach to the Unibus goodies with a Plessey Quniverter. 18 bit only but more than enough to replace an 11/34.
Click to expand...

This is what is on the back of the Q-Bus backplane. I don't find anything about it with Google. There isn't a manufacturer's name or logo on it.

1761857132859.png
 
Henk said:
And with the stack limit option (a simple "single width" board), you probably need the MMU as well.
Note that the 11/40 requires jumpers on several boards to be wrapped correctly when adding options to the CPU.
IIRC, for the KW11 (line time clock) you even need to do some work on the 11/40 backplane!
Click to expand...
We have a BA11 chassis that contains what was supposed to be a running PDP-11/35 - 11/40. The 9-slot processor backplane has all possible CPU options installed, including the KW11-L. I believe that the 60 Hz clock signal from the power supply is routed to the power backplane. I will have to see if it is routed through the power cables to the backplane. There is also a KW11-P programmable clock in the chassis.

We will add an RL11 disk controller, TC11 DECtape controller, and probably a DEUNA board set.

1761857472502.png
 
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m_thompson said:
We just started a PDP-11/40 project at the RICM. We got the system from Fairfield University who got it from yale University. Yale gutted the system and installed a hex-wide Q-bus backplane, 11/23 CPU, Memory, 4x Serial Ports, and GPIO cards. They even made a wire-wrap board to interface to the 11/23 CPU.
Click to expand...
It would nice to see the 11/40 returned to its former glory.

Is there any documentation or schematics on the interface to between the QBus and 11/40 Front Panel? I'm curious what signals they were able to utilize and what approach they took.

I happen to have a 11/40 front panel and a spare 11/23 system. I would love the opportunity to duplicate the board, even if it's just a wire-wrap implementation. It looks like an MDB MLSI board, which has the Q-Bus interface already etched, was used. I wonder if any special software was used to enable it.


Jerry
 
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wa2flq said:
It would nice to see the 11/40 returned to its former glory.
Click to expand...

That is our plan.

wa2flq said:
Is there any documentation or schematics on the interface to between the QBus and 11/40 Front Panel? I'm curious what signals they were able to utilize and what approach they took.
Click to expand...

Not a bit of documentation came with the system.

wa2flq said:
I happen to have a 11/40 front panel and a spare 11/23 system. I would love the opportunity to duplicate the board, even if it's just a wire-wrap implementation. It looks like an MDB MLSI board, which has the Q-Bus interface already etched, was used. I wonder if any special software was used to enable it.


Jerry
Click to expand...

I will take pictures of the front and back of the board on Saturday. It doesn't look complicated enough to implement much of the front panel.
 
m_thompson said:
This is what is on the back of the Q-Bus backplane. I don't find anything about it with Google. There isn't a manufacturer's name or logo on it.
Click to expand...
That really looks like a DEC backplane. The 54-12038 would be the correct part number for the PCB. I'd expect to see a paper label on one edge or the other with inspection stamps, revision info and possibly a product name. I'm thinking it may be from the CSS group.
 
m_thompson said:
We have a BA11 chassis that contains what was supposed to be a running PDP-11/35 - 11/40. The 9-slot processor backplane has all possible CPU options installed, including the KW11-L. I believe that the 60 Hz clock signal from the power supply is routed to the power backplane. I will have to see if it is routed through the power cables to the backplane. There is also a KW11-P programmable clock in the chassis.
Click to expand...
OCR'd from original image >> The installed boards are:

1. M7239 KE11-F FIS Option
2. M7238 KEll-E EIS Option
3. M7232 KD11-A U Word
M7237 KJ11-A Stack Limit
M787 KWll-11 Line Time Clock
4. M7231 KD11-A Data Path
5. M7233 KD11-A IR Decode
6. M7235 KD11-A Status
7. M7234 KD11-A Timing
8. M7235 KDll-D Memory Management Option
9. M981 Unibus Jumper
M7800 DL11 Asynchronous Line Interface Board
10. M981 Unibus Jumper
M7228 KWll-P Programmable real-time clock
11. M7891-DC MS11-LD 128kW X 18 bits (256KB) MOS Memory
12. M7800 DLll Asynchronous Line Interface Board
13. M7060 LKlO VT48 push button control for the LKll Button Box
14. M7860 DR11-C M786+M105+M7821; general device interface
15. M8256 RX211 RX02 floppy disk drive controller
16. M9202 Unibus Jumper
M8730 KHll-C Calendar and clock module
17. M9202 Unibus Jumper
M9312 Bootstrap/Terminator DY, RL02, and ASR33/PC05 boot ROMs
18. M7014 VTll Unibus Controller and Bootstrap for VT40
19. A320 VTll Vector and Character generators, and D-A convertors
20. M7013 VTll Vector Generator and Character Generator Control for VT40
 
We decided to use a newer 21" expansion chassis that was in the warehouse. We removed it from a short DEC cabinet and installed in in a full height cabinet along with a DEC power controller. This chassis has broken AC wires to the fans in the power supply and is missing some sheet metal that holds the upper fan tray. We have the missing parts in one of the unused expansion chassis in one of the PDP-11/45s in the warehouse.

Our leader Dan said this might be a good system to demonstrate our TA11/TU60 DECcassette drives. That sounded like a good idea, so we dug the TA11 out of the warehouse for later installation once we find a set of slides for it. I bought controller for the TA11 on eBay a while ago.

The current idea is install a 5 1/4" or even a 10 1/2" filler panel above the PDP-11/40 so the hot exhaust air has somewhere to go. We would install the VR14 and the TA11 above the filler.

We noticed that some of the PDP-11/45 cabinets have two large exhaust fans in the top, and some just one. We currently have just one. I wonder if two fans would be better.
 
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Today we checked out the power supplies and added an upper fan tray. All three H744 +5V regulators are working, the single H745 -15 regulator is also working. Since we won't have core we need to swap the H754 +20V/-5V regulator for another H745 -15 regulator. One upper fan and one lower fan in the CPU chassis are seized. It looks like the AC LO and DC LO signals are both active (low). Maybe it needs a pullup from the CPU that is not installed? The Line Clock signal measured 2.27V with a DVM, so it is probably active.
 
m_thompson said:
We noticed that some of the PDP-11/45 cabinets have two large exhaust fans in the top, and some just one. We currently have just one. I wonder if two fans would be better.
Click to expand...
Sure but whether "necessary" is another matter, dependent on the usual considerations (module complement, rack load, side panels, ambient temperature). A second fan won't hurt ... but it will add more of that classic machine room audio ambience :-}
m_thompson said:
Today we checked out the power supplies and added an upper fan tray.
Click to expand...
What did you do for the check? Sounds like you didn't dismount and reform the electrolytics ...
 
pbirkel@gmail.com said:
What did you do for the check? Sounds like you didn't dismount and reform the electrolytics ...
Click to expand...
We did a no load check after a quick capacitor reform with the capacitors in place. We still need to check the ripple on the outputs to see if the filter capacitors are filtering. At this point I was more interested in determining if the regulators actually worked than determining how well they perform.
 
We spent some time Saturday fiddling with fans. One of the upper fans was binding so we took it partially apart and sprayed it with WD40. That made a mess when it spun up, but al least it ran. It would not start after a power cycle. The two unused 21" chassis that we have been using for parts don't have any fans left, so we will need to hunt in the warehouse for another chassis that can donate fans. I know where there is a BA11 chassis. Maybe those fans are the same?
 
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