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Thread: Got a PDP 11/83

  1. #1
    Join Date
    Jul 2009
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    Default Got a PDP 11/83

    I was just gifted with a PDP 11/83. It's a rack mount dual chassis unit. It has a floppy and tape drive and 2bays for hard drives. I looked on bitsavers, they don't list this machine. Since it's very heavy the previous owner tried to separate the 2 chassis. They are connected together with a frame, and a hinged back panel. Inside the back cover there are many ribbon cables, some of which have been disconnected. I can't open the hinged cover very far as there are a large number of serial ports on it. I can see where one of the cables goes, but there are 3 others that look to go to cards. One is marked "tape". I will be taking some pictures over the next few days.
    Does anyone know: what the proper way is to open that back cover? What hard drives should I look for? Which serial port should I connect to to get a console? I'd like to run UNIX on this, will I find the distro and can I get it to the DEC's floppy format?

    Thanks for any help,
    Kipp
    Looking for: Altair 8800, Ithaca Intersystems boards, software, manuals. and Jade bus probe card.

  2. #2
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    Hey! Welcome to the 11/8x club.
    Yeah, it sounds like photographs would be a good start. I'm having a tough time seeing your system in my head.
    = Excellent space heater

  3. #3

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    Quote Originally Posted by NeXT View Post
    Hey! Welcome to the 11/8x club.
    Yeah, it sounds like photographs would be a good start. I'm having a tough time seeing your system in my head.
    Same here. I wanna see some pics.

  4. #4
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    The 11/73 and 11/83 use the same CPU with different memory configurations. The KDJ11-B CPU Module User's Guide (EK-KDJ11B-UG-001) from bitsavers will be a big help in getting started with this system.

    Jack
    Last edited by jackrubin; August 24th, 2011 at 04:18 AM.

  5. #5
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    Default Pictures of the PDP 11/83

    Here are some pictures
    DEC PDP 11-83 055.jpgDEC PDP 11-83 056.jpgDEC PDP 11-83 057.jpgDEC PDP 11-83 058.jpgDEC PDP 11-83 059.jpg
    The 1st picture shows it with the covers on, when I took them off I found the dual floppy drive hidden there (see 5th picture).
    The previous owner said it worked before he removed the cables in the back. I have not yet powered it on.
    The 2nd picture shows the rear door. It's hinged, has 2 7-segment displays, 12 serial ports, some ports at the bottom that I don't know, and the port under the 7-segments that I think might be the console.
    The cables that have been removed either go to or come from the rear door. I can see where 2 of them go, but not the other 2. I also see that one of the 1/2 width cards in the upper rack is out of it's slot and tipped toward the metal bottom of the cabinet.

    I wanted to open this door, take pictures, remove and clean the cards and chassis, and then reassemble. The door won't open farther than it is due to the cable routes.
    Kipp
    Looking for: Altair 8800, Ithaca Intersystems boards, software, manuals. and Jade bus probe card.

  6. #6
    Join Date
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    Default

    Quote Originally Posted by kyeakel View Post
    What hard drives should I look for?
    There are no hard disks in what you have. If you're lucky the controller driving the
    floppies can be used in the top chassis where the MFM controller cables are coming
    out to the front.

    'tape' is for the TK50 tape drive in the lower chassis.

    This system probably had RA series external drives connected to it through the
    small connectors on the back panel.

    There is going to be a fairly large disk controller board connected to those small
    cables on the back.

  7. #7
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    Wow, those are some big power supplies! Have you turned it on yet?
    ~Ian~

    Looking for a Gateway 2000 G6-333 - my first computer.

  8. #8

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    If you haven't already, please go no further with your current disassembly efforts, and whatever you do, DO NOT plug it in and TURN IT ON.


    Some general comments...

    The boards in this assembly have no protective coatings, so please carefully return the top cover, and re-fasten it in place to prevent accidental contamination. [ That's a memory board there BTW ]


    Everything you need to do should be accessible from the rear.

    What you have there is two BA23's coupled together in that assembly. [Ganged together for I/O space and power] A special back panel is placed across them, which has been partially removed in the wrong sequence. [which is why you're having difficulty now] Note the safety tether wires dangling down, disconnected in this pic. These were meant to take the weight of the removable rear cover.


    To proceed safely, please locate another "table" slightly lower than, but in addition to, the one it's now resting on, and position it to receive the rear panel assembly. [It's too heavy to hang by it's ribbon cables]

    Once that is done, try removing the two screws in the upper right corners of the rear panel.



    This should free the cover. Lay it face down on the new table, exposing the cables that connect it to the individual PC boards.

    ------------

    This will get you to a safe place, where we can help you identify the boards in your machine. My quick assessment would be that it may contain two RLV12 controllers, that I doubt you will be able to locate RL01 or RL02 drives for. These are probably the two black connectors along the bottom of the rear panel.

    I think this unit once contained it's internal hard drives [RD series?] in the upper bay [a few MFM and power cables remain there]

    BTW: The floppy drive "hidden" in the lower bay, may have a boot floppy in it. Have you checked?


    In summary, depending on what you want to accomplish, you may be able to re-arrange that equipment and run the a UNIX system from the floppies, with only one of those BA23's powered. [keep the other as a spare?]

    If you decide to continue disassembly, please take copious photos as you do, so we can tell where the cables go back - in case you need them. Don't pull any cards until you have complete notes on where they were, and how they were cabled in this original configuration. [photos again, are best]

    Hope these hints help. Looks like the ingredients of a nice system.

  9. #9
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    Feb 2011
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    Salisbury Maryland
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    Is that still a Qbus style system? Would assume it’s a 22 bus as opposed to a 16? What's the progression from my 11/03 and 23 to that system and finally VAX? See lots of cards on EBay that are to new for the 16 bit 23 system and too old for VAX or that’s what I assume not have ever seeing a VAX up close and always though they were 73/83 cards.

  10. #10

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    Quote Originally Posted by Qbus View Post
    Is that still a Qbus style system? Would assume itís a 22 bus as opposed to a 16? What's the progression from my 11/03 and 23 to that system and finally VAX? See lots of cards on EBay that are to new for the 16 bit 23 system and too old for VAX or thatís what I assume not have ever seeing a VAX up close and always though they were 73/83 cards.
    Yes, it's made of two BA23 boxes with Q22 backplanes [these may be decoupled and turned into independent systems if desired]

    The BA23 can be used for any Qbus processor... PDP-11/02,03,23,73,83 and Micro-VAX I or II, provided power needs are met.

    Cards of the generation found in original 83 systems will probably be useful in Qbus Micro-VAXs. This includes the PMI memory in the photo and many I/Os, but obviously not the CPU.

    I'm not sure what you're seeing on eBay.

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