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Beginning with PDP-11 stuff

C

Christoffer

Experienced Member
Joined
Oct 15, 2014
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299
Location
Denmark
Hi! I have a couple of question about PDP-11 hardware, I'm hoping some of you would help clearing up:

An actual PDP-11 has been my far-out dream system for a while now, and I'm still looking at information on what's possible or not.

I'm definately gonna build/assemble a minimal system of boards as a first, but I'm not hugely in on the PDP-11 architecture yet.

These KDF-11 pdp-11 LSI CPU QBUS boards that are up for sale once in a while seems like a logical place to start. They typically has the FONZ-11 processor and one or two other 40-pin chips.

Now would one of these two-chip CPU cards work as is, if given some RAM and a serial port?
I understand the LSI pdp processor chips has an octal debugger you'd be able to talk to. Do they all have this, or is it exclusively the J-11?

I know "pdp-11" is an entire family of machines, but at first, I'm not picky as of which model I'm going for.

Thanks in advance,
 
Hi All;

Christoffer, I am not a Qbus person, but a Unibus person..
So, having said that I think that You are correct.. Adding Ram and a Serial I/O card will get You a working system.. Along with a Power Supply..
But, You need to hear from QBus or one of the others who know more specifics on these particular systems..

THANK YOU Marty
 
I bought my first PDP-11 system back in the mid 1980's at a salvage price. Those days of cheap DEC hardware are for the most part behind us. That having been said, "barn find" bargains still turn up from time to time so keep your eyes open at ham fests and places like Craig's List.

If I were to start over again I would first focus on QBUS systems. But that's like saying "IBM compatible" in PC world. IBM made a lot of different PC's and their guts don't always play well together. Simply put, get the newest, most complete, most working system you can afford. Buying a random collection of boards that may not play well together may well cost more in money and certainly more in frustration in the long run than a reasonably complete system. Look for something like this:

http://www.cosam.org/computers/dec/pdp11-23/logic.html

QBUS systems came in many variants from DEC and various OEM's. There's a wide variation in backplanes you need to watch out for. They were made with 16, 18 and 22 bit address busses. Some can be "upgraded" if you're reasonably handy at soldering. You'll see terms like A/B/C/D and A/B/Q22 along with serpentine or straight. My goal would be to find a BA11 box with a 9 slot A/B/Q22 backplane but in the real world sometimes we start out with what we can get.

Good luck!
 
The easiest way to get started is a CPU card, some quantity of RAM, and a SLU board. The DLV11-J four-line SLU will give you console, and allow for an emulated TU58 drive to boot from on SLU0. You could use two single DLV-11 SLUs as well, but the DLV11-J is very convenient, and not too expensive. My first PDP11 was a LSI-11/2 CPU board, 32KW RAM on a MSV11, and a DLV11-J for console/TU58 in a little 4-slot dual width backplane I found in some old lab equipment.

DDS's second link includes instructions on how to make a minimal "front panel" for a bare backplane, providing RUN/HALT functionality and DC OK.

PM me if you're having a hard time finding cheap QBus boards. I have a *lot* of spare QBus stuff I need to go through. Not so many KDF-11 CPUs but lots of KD11 LSI-11/2 CPU boards and many DLV11-J SLU boards.
 
No doubt I'd prefer just to find a "barn find" - but PDP-11's weren't massively popular in Denmark.

but in the real world sometimes we start out with what we can get.
Click to expand...
Exactly why I thought getting ANY cpu card, and then speccing my expectations from there were a good idea. Could even put the rest of a minimal system on a breadboard if I had to.
The easiest way to get started is a CPU card, some quantity of RAM, and a SLU board. The DLV11-J four-line SLU
Click to expand...
That's what I thought. The main issue is finding these boards in Europe. It gets really pricey fast if you need them sent from the rest of the world.

The backplane sockets are 0.150 pitch card-edge connectors, right? You could do without a proper DEC backplane.
 
I have a spare QBus backplane (not sure if it's 18-bit or 22-bit, but I suspect the latter) if you want, but I don't know if you want to bother shipping internationally.
 
Being in Europe, you should probably take note of the Soviet "Elektronika" PDP-11 clones as well.

You really have to determine what aspect of the PDP-11 interests you the most. If it's just the machine architecture and running programs and not grubbing around with the iron, you may want to consider starting off with a FPGA clone, such as PDP2011 and a whole host of other FPGA implementations. AFAIK, all will run RSX-11.
 
That's good to know! Are these Elektronika's fully compatible? like, boardwise copies?

It's definitely the hardware part that interests me the most. I didn't mean to imply that I didn't care about the hardware, just that I can't be very picky.

I have a spare QBus backplane (not sure if it's 18-bit or 22-bit, but I suspect the latter) if you want, but I don't know if you want to bother shipping internationally.
Click to expand...

That sounds very good, but again the issue with international shipping, import fees and such It'd get very nasty.
 
Christoffer,

There is a very vibrant PDP-11 community in Europe as well and I'm sure some of those folks will check in here. There are very active, friendly and helpful folks near you in Sweden, Holland, Switzerland and Germany and some I'm sure there are some in Denmark as well.

Jack
 
"You could do without a proper DEC backplane."

With some wire wrap versions of the proper connectors and a suitable platform to mount them on you'd be a few evenings with a wire wrap gun short of a functioning backplane. Take a look at some of the stuff Marty has created. Compared to the PDP-8 clone he's been building a backplane would be a walk in the park. Just be careful with your power leads. You're going to be routing some non-trivial current. I believe you should look at the link I posted for Diane Neisius' page for pointers on how he adapted a pretty much standard PC power supply and a built a front panel simulator.

I've done stuff like that in the S-100 world but always wished, at the time, that I had a proper box to put it all in. So keep your eyes open for some of the "good stuff" to pop up near you. I'm sure there's a PDP-11 collector in Denmark that has extras of what you're looking for that would give you a decent deal to get you started off right. Find out where they hang out, in the real world or a virtual one, and make your interest known.

Good Luck!
 
Chuck(G) said:
Elektronika stuff is probably not board-level compatible, but I'm willing to be corrected on that. The chips wound up in a bewildering array of equipment, right down to a pocket calculator and home computers.
Click to expand...

It's maybe electrically compatible but definitely not board-compatible -- connector pin spacing is different (metric vs. non-metric).

Speaking of Soviet pdp-11 compatible home computers, I'm currently working on a MAME driver for a few of those -- mostly because they have frame buffers and games :)

Some progress:

Chess game with board display
 
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