View Full Version : Looking for service manual for MicroPDP 11/73

December 21st, 2008, 07:46 AM
Like I wrote in my collection-thred I've gotten my mits on a MicroPDP 11/73... No documentation was included, and this is my first DEC ever. :oops:

Any kind of manual for the machine would be nice, especially the service manual.

Config is 3 MB RAM, RD51 MFM drive (10 MB) and a J11 @ 15 MHz. As for expansion cards I'm not sure, but I was told that there should be an ethernet interface...

Lou - N2MIY
December 21st, 2008, 11:29 AM

You won't fiind an "everything in one book" manual for your 11/73. However, if you take the back door off and make a list for us of all the boards in the machine, we can help you find the manuals for the individual boards.

So far, you at least have an M8190 board (the 11/73 processor). The manual for it is EK-KDJ11B-UG-001. You'll find it in here: http://www.bitsavers.org/pdf/dec/pdp11/1173/ .

So, list out the M number cards. I too have an 11/73 and went through this quest myself a couple years ago.


December 21st, 2008, 12:25 PM
Thanks for replying Lou, as a matter of fact I've finished my list of all the boards inside. :)

M8190-AB KDJ11-B CPU 5016017-01-D1-P3 Qbus Quad Wide uPDP-11/73 CPU (DCJ11-AC 57-19400-04) J11 CPU, 15MHz with 2 boot & diagnostic ROMs, FPJ11 compatibility (warm floating point, but will accept FPA)

M7551-AC MSV11-QA 5017547-01-C1-P2 Qbus Quad Wide 1-Mbyte 22-Bit PAR CSR MOS RAM M7551-CA

M8067-KC MSV11-PK 5014500-C Qbus Quad Wide 256-Kbyte MOS Memory with Parity CSR

M8067-KC MSV11-PK 5014500-C Qbus Quad Wide 256-Kbyte MOS Memory with Parity CSR

M7551-AC MSV11-QA 5017547-01-C1-P2 Qbus Quad Wide 1-Mbyte 22-Bit PAR CSR MOS RAM M7551-CA

M7555 RQDX3 5016674-01-D1-P2 Qbus Double Wide Winchester and Floppy Disk Controller (RX50/RD50-54/RD31/RD32)

M9047 Bus grant card


I've found a manual for the DEQNA-card. And some kind of maintenance guide for the 11/73 (document id EK-MIC11-SG.001).

Seems like just 2 MB of RAM. Might have missed one card there. Lots of cables in front of them. :]

There was also another card next to the M9047, unmarked with black handles and green PCB. Didn't seem to have much components on it. Any ideas? Maybe just a placeholder/dummy...

December 21st, 2008, 02:02 PM
Fun to see that you got going with the PDP so soon :) I know Vol has been having fun with his new SUN gear too.

Anyways, the M9047 is a bus grant. It is basically a dummy. You are lucky to get a long one :) The short ones were called "knuckle busters" because you scratch you knuckles on adjacent cards when inserting them. Also I count 2.5 MB of ram?

Here is a list of cards: http://world.std.com/~mbg/pdp11-field-guide.txt

Otherwise, bitsavers are your friends.


December 21st, 2008, 03:09 PM
Ah, good thing the stuff came to use! :) You shoud try to lure him and burbas over here. I was all over the PDP the minute it arrived in my appartment.

I think this is the short bus grant, it is only half the width of some of the other cards. The unmarked card sits to the left of it. :/

And yeah, you're right about the RAM. Somehow I thought that the M8067:s was ROM or something... :lookroun:

Lou - N2MIY
December 21st, 2008, 06:50 PM

Looks like an excellent system. You do have 2.5MB (1.25 MW, 16 bit words) of parity memory there. You are ready to roll with RSX (it needs parity memory). The max you could have in there is 2 MW.

The RQDX3 is excellent. You can add easy to find Seagate ST-225 (dec RD31) and ST-251 (dec RD32) on that controller (among other disks that dec resold under their own model numbers.) When you're ready to add another disk, let us know, there are tricks (correct jumpering, how to format.)

The deqna is good also. You'll need an AUI to 10BaseT transceiver.

You could use one more SLU (serial port). KDJ11-B has only one SLU (the console). You'll want another for a serial printer or connecting an emulated dec TU58 dectape II drive.

Maybe the card with the black handle was another SLU? Pull it out and take a photo for us, so we can see what connectors might be on that card and what the chips are.

Don't worry about some cards being quad height (like the processor) and others being double height (like the RQDX3). However be aware that there is some amount of reason behind the way the cards are ordered in the backplane. Also, the top three slots are special. Get a copy of EK-OLCP5-TM-002 here: http://bitsavers.vt100.net/pdf/dec/qbus/EK-OLCP5-TM-002_microPDP11tm_Jan84.pdf and read up. This document was "everything in one book" for the Micro-11/23. The 11/73 uses the same mounting box and backplane, so that information still is valid.

You can find the other manuals for all this on bitsavers.

Did you connect a console terminal and boot it up yet?


December 22nd, 2008, 04:02 PM
Thanks! :) I'm thinking of RSX-11M (or should i go with plus?) for the machine. I'm not looking to do anything special with the machine in the beginning, just exploring the new OS and learning about the hardware.

Later on I'll probably try to get some sort of network service running on it. I'm thinking about a gopher server. It's part of a futurama joke that I keep pushing... The machine is named Farnsworth, and I have a Sparcstation 4 named Wernstroem. Given that Farnsworth is a bit older than Wernstroem this is all good. And if Wernstroem runs a webserver, Farnsworth must run gopher of course.:happy2: Oh, bless the nerd humor... Any ideas of taking this further, perhaps the PDP should limit itself to just DECnet? That would be a waste of the DEQNA though. I have several AUI to TP, BNC and 10BaseF converters for it.

I'm guessing that a TK50/70 won't work on the RQDX3? Had some plans of filling the empty slot in the front with something and a tape drive is always to be desired if you ask me.

Yes, another RS232-port would be neat. I have eight more DB25 connectors on the back, but I think the cables for them was disconnected. I don't see an expansion card for RS232 in the list.

Photos of the card (and of the whole machine of course) will be fixed soon. I'll just have to find the time to get apache running on Wernstroem... :p

Thanks for the link, always nice with some reading material now when my short vacation comes around!

Sadly I haven't got around to boot the system yet, but I will solder together a DB25->DB9 cable for the console. When I have the energy to repair the abused keyboard contact in my VT420 I'll run it for the console of course!

Lou - N2MIY
December 22nd, 2008, 04:27 PM

The empty slot in the front was usually filled with an RX50. I assumed there was one there, but it looks like you didn't get it. Similarly, if there are eight more DB25 connectors on the back panel, this machine at one time had a DHV11 (M3104) serial multiplexer for connecting the user terminals. My 11/73 had this and ran Micro-RSX when I got it. (The RD52 broke beyond repair and when I replaced it I switched to RT-11 and didn't look back.)

I suggest you fill the open hole with two Teac FD55GFR 5.25" floppy drives. These were dec RX33s and are pretty common (cheaper and more versatile than an RX50.) They connect directly to the panel in the back of the bay.

As for the TK50, you could use that, but you need a TQK50 or TQK70 controller (they don't connect through the RQDX3.) I have a TK50/TQK70/tapes but have never run it (because I don't have a new enough version of RT-11 that has the handlers.) From what I understand, it's just not worth the trouble (the internet is filled with TK50 horror stories.) I back the machines up over ethernet.

I'm not very familiar with RSX-11, so someone else will have to provide you with the help there. I use RT-11, which is very forgiving to an amateur like myself. A single user OS is all I need (since my wife has no interest and kids are too young to appreciate it.) Maybe you should consider starting with whatever is on that RD51 first.


December 22nd, 2008, 11:54 PM
The local PDP-guru seems to think that RSX-11M+ is the way to go :) But for me the jungle of OS:es for PDP-11 is confusing, perhaps 11M is just as good... or RT-11 or CP/M or ...

Well, RSX-11M is somewhat similar to VMS if you have any experience with that. You can always login to "mim.update.uu.se" for a hands-on experience with an emulated 11/70.

I suggest you subscribe to the cctalk mailing list (http://www.classiccmp.org/). Be patient though, I had to try at least five times before I got on the list :P

Also checkout HECnet: http://www.update.uu.se/~bqt/hecnet.html

Happy hollidays.

December 26th, 2008, 01:56 PM
Finally got around to fixing Wernstroem and his 911-box (only 3 disks worked...). Pics can be found here: http://cl3m.net/disk0/2008.12.21-MicroPDP1173/

I'll have to think about the OS choice for a while. The guy who owned this machine before me offered me some help. I think the disk is empty, so I'll wait.

Good point about the TK50, I'm guessing that a <20 year old tape drive could have some issues... :) I found a RX50 at ebay for $15, seems like a good price. No RX33s though, seems like they have the double capacity (2 MB)?

Tried to get in to cctalk once, and got denied without an explination... But I'll try again. :) Seems like a good knowledge base.

Of cource I will join HECnet! Seems like a noble project. Is there a list of connected computers?

Lou - N2MIY
December 26th, 2008, 05:25 PM
You can't format disks in an RX50. Unless you have exitsing RX50K media, you'll have to format your disks elsewhere. The RX33s are not that hard to find and are often cheaper (for two) than one RX50 (and can format disks). The key is not to buy something labeled as RX33, instead by TEAC FD55GFR drves.

cctalk is interesting. I've tried myself three times over the past year to join, with no success. I do read it daily though, and have written to people off list. I'm not sure why it's so difficult to join. I guess you have to know someone.

The core 11 folks are on alt.sys.pdp11. They are a good bunch and also very helpful.

The machine looks good and clean from the photos!


December 27th, 2008, 02:57 AM
A HECnet node list... hmm

*dig* *dig*

ah, here it is:


lots of hardware in that list

December 27th, 2008, 08:32 AM
You can't format disks in an RX50. Unless you have exitsing RX50K media, you'll have to format your disks elsewhere.

Actually, you can format RX50's (including low-level) if you have a DEC Rainbow. As far as I know, its actually the only RX50-based system that can do this. I regularly use double density disks in my Rainbow after formatting (requires MSDOS 2.11 i believe). Of course, they format into a RX50 400KB single-sided disk.

The problem is not the RX50. The problem is DEC and their desire to sell preformatted media. The Rainbow engineers had enough foresight to ignore the rest of DEC and allow formatting. The limitation is purely software (maybe controller chips too, I'm not sure).

Lou - N2MIY
December 27th, 2008, 10:10 AM

You're right - floppies can be formatted in an RX50 if it's on a Rainbow. I forgot about that (and I used to have one too.)

I had heard though (maybe a dec created myth) that the mechanism inside the RX50 was not precise enough to reliably format disks. I have torn down and put back together RX50s on two occasions, and to my eye, it does look robust enough. Perhaps you're right that it was a ploy to sell media.


December 29th, 2008, 09:39 AM
I had heard though (maybe a dec created myth) that the mechanism inside the RX50 was not precise enough to reliably format disks. I have torn down and put back together RX50s on two occasions, and to my eye, it does look robust enough. Perhaps you're right that it was a ploy to sell media.

I am close to a member of the Rainbow engineering team who was at DEC in the '80s, and he stated quite definitively that it was nothing more than a marketing ploy to sell RX50 media. Don't believe DEC's hype ;)...