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Getting a DEC PDP 11/03-LX

M

mham

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Aug 26, 2013
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17
Hey all,

Posted a lot back in the summer of 13 looking to get a DEC PDP. I've got the opportunity to buy a DEC PDP 11/03-LX for $400 shipped. It's in great condition, but I'm sure I'm going to be on here asking for some help from you all at some point or another. Anything I can start looking at or reading now to get an idea of what I can do with this machine/ familiarize myself with it.
Thanks!
-Mike
 
Hi All;
Mike, I do not know an 11/03, But I think it is a Qbus Machine, (QBus would know for sure) since I am a UniBus Person myself.. But, I would get the HandBook for it and Anyother files that BitSavers has on it and on anything in its relative Family, and start taking a look at all of it..
THANK YOU Marty
 
The 11/03 (which I know quite well) is an LSI-11 bus device. I have just purchased a set of cards for an 11/02 and I am just about to start to get them commissioned - so we should have quite a lot in common. Not sure what the "LX" means. I will look it up a bit later.

I found a document on good old bitsavers which contains a section on the 11/03 (see http://bitsavers.trailing-edge.com/pdf/dec/pdp11/1103/EK-LSI11-TM-002.pdf).

I am going with an 11/02 processor (with FIS/EIS option), MSV11-DD 32KW memory (or more correctly 30KW allowing for the de-configured I/O space), DLV11-J quad serial card, M9400-YA terminator/bootstrap card, and an RXV11 disk interface to an RX01 floppy drive. I am using my Raspberry Pi as a VT100 console and I have just completed a Python emulator for the RX01 drive which I will fit to the RXV11 controller via a simple 3.3V to 5V level shifter circuit.

I was unable to acquire a reasonably-priced 8-slot LSI-11 backplane - so I obtained some connectors and will be wire wrapping one myself (using a PC power supply for +/- 5V and +/- 12V).

Dave
 
Think I would ask what cards are in the system first, it’s easy to read them directly off the tabs in the back. Almost every 11/03 I have seen has been converted to a 11/23 with the replacement of the CPU card with a KDF-11 or 8186 card, you will also need some sort of a Async car preferably with four ports, one or two memory cards and my favorite the BDV-11 Bootstrap, diagnostics and terminator card. All of this is not including what you would need for a floppy or a RL controller. Also have to remember that with a 03 or 23 that they don’t like 22 bit cards stuffed in them so avoid the newer series cards and large memory cards that are all around.
 
Daver2,

I too am very interested in your Raspberry PI RX01 emulator. I have a PI also and would love to put it to good use! At this very moment, I am troubleshooting an RX01/RX8E that I am finally putting in my 8/a. An emulated RX01 would take up a hell of a lot less space!

Do you have a project writeup somewhere?

Lou
 
No project write up anywhere yet. I am finishing another project off first (which I have just done - reverse engineering the software protection chip out of the Commodore SuperPET) so I am just writing up how it was done and putting that up on the website first.

I had bought the LSI cards just before Christmas along with a dual height 4 slot LSI backplane and cardcage. The cards arrived, but the backplane supplier took my money and then said he couldn't be bothered to ship my backplane :-( A swift e-mail to PayPAL got him to refund my money - but that is not the point. The LSI card supplier said that he had some wire-wrap backplane connectors that he would throw in - hence the reason I am going to knock up my own backplane (although I have just done a deal to obtain a load of equipment for work and there are some 11/73's there going begging - a post will duly be put up if the lead pans out for anyone who is interested - but I am having a backplane).

My 'plan' for the PI is as follows:

RXV11 disk controller connected via the ribbon cable to a 5V to 3.3V converter board (as the PI only likes 3.3V signals and dies otherwise) connected to the GPIO connector of the PI. The interface will initially be knocked up on breadboard - with the ultimate aim of transferring it to a plug-in card for the PI so it is a little bit more professional than a dangly mess of wires - although I am not planning to make a bespoke PCB. If anyone would be interested in making a PCB I will be publishing my schematic diagram (in exchange for a PCB of my own of course).

The software is pretty much already written in Python. I launch a Bash script from an icon on the desktop and it runs the python interpreter (as root because it needs access to the GPIO ports). I specify on the command line one or two filenames (which will obviously contain the RX01 disk images) and an optional number specifying the amount of diagnostic information that is produced during runtime when processing commands from the RXV11. Python is a scripted language so you get all the source code so if you don't like what I have done - you can change it. The approach I have so far taken is to read the one or two disk images supplied as command line parameters into memory and to let the RXV11 'play with' the memory copy. I have done this initially so that if something goes wrong with the 'sector write' code it won't corrupt the file images on the disk. I will think later (when I am happy that things work) about writing the memory back to disk. Obviously, if the filename specified is write protected then this should signify to the emulator that the file is read only...

I think most of the Python code is there - but I am a little bit confused about the status return back from the RX01 microcontroller to the RXV11 card at the end of a command. Can anyone point me to a more fuller description of the registers of the RXV11? I have a pretty good write up of the RXV12 - but not the RXV11.

The limitation of this set-up is that you can't change the disk images on the fly. So, I have started to add a graphical user interface using Pygame. I have currently got an image of the RX01 drive with little images of floppy disks with their contents labelled beside the images. I am currently working out how to drag and drop the disk images onto the image of the RX01 drive... And yes - it does make a noise... So, that's my ultimate aim - a text file describing the 'disk contents' which will appear as a scrollable list of little floppy disk images with their contents. Each one specifying a Linux file actually holding the RX01 image itself. Drag and drop to one of the drives of an RX01 image. You will have to 'eject' anything that is already loaded (just like the real thing) before inserting a new disk. If the Linux file is read/write (and the image has been written to) any sectors that have been modified would be written back to the disk image before the disk is ejected (or the emulator terminated).

Having said that - I still don't have any LSI to get it to work on yet! If anyone is interested in doing some work themselves - PM me and I will quite happily share the code with you.

It would appear as though the RXV11 can have up to an 8 bit track and sector address. At the moment the DX driver 'knows' there are 77 tracks and 26 sectors of 128 bytes (FM). One possibility is to increase the track and sector limits to 255 each within the RT-11 driver (changing the name from DX to say EX) which should make a disk size available of 8 MB or so!

All these are way in the future so I will stop daydreaming now - but that is my intended goal.

Dave
 
Forget to say - I am only supporting the RXV11 on LSI bus at the moment. This simplifies my software somewhat. If you want to support the '8' then I will have to include the hardware line for the 12-bit transfers. I will add this to my hardware list but I will leave the software out until I get my emulator working with my 11/02. I can then start to 'complicate' the software by adding support for the RXV12 and '8'!

Dave
 
Thanks everyone for the responses. I don't know much else about the system yet, I haven't actually bought it but I can I am waiting for more info. I'll post it here as it comes so you can get a better idea of the system.
 
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