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Thread: PDP-9 at the RICM

  1. #1
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    Default PDP-9 at the RICM

    Tomorrow the RICM is moving the Lab to new+ space that is about twice the current size. That means that we can haul some more interesting items out of the warehouse and into the Lab. First on the list is the PDP-9 and the cabinet with the TC59 mag tape controller, and the TU20 7-track tape drive. Charles Lasner donated a TC02 DECtape controller, and we can borrow a very early design TU55 from the PDP-8/I.

    The last time we ran the PDP-9 it would run the built in self test from microcode, so we know that lots of the processor is functional. It would also load a paper tape diag, which is also done from microcode. When we tried the memory checkerboard it went off into space. We can read/write memory, but doing that from the console doesn't mean it will work when the processor is running. Our plan is to try some very simple instructions to make sure that the processor can actually decode and execute instructions. If that works, we could try some more complex instructions like ISZ and JMP. If it is still working then we could try running the instruction tests from paper tape.

    Once the processor is working again, we will connect the TC02 to the I/O bus and see how much of that works. We can repair and test the ancient TU55 on the PDP-8/I before we move it to the PDP-9 so we don't make debugging even more complex. If we can get the TC02/TU55 working we should be able to get a DECtape based OS running. That would be very cool.

    The processor manual says that it has four data channels for devices like DECtape and magnetic tape., so it looks like we can connect both the TC02 and the TC59 without having a DM09, like you would need in a PDP-8. I wonder if we could hack the OS and run serialdisk?

    We also need to rewind the sensor coil in the PC04 paper tape punch so we can get that working.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  2. #2

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    Congratulations to the new space! Much easier to work with it when it is in a heated space.

    It will be very interesting to follow your work on the PDP-9. But it did work quite well at some point, didn't it? I remeber some video clip that it read from mag tape.
    My experience with our PDP-9 is that it also was breaking down quite often. This was 20 years + back. I remeber that I replaced the same transistor on a certain card a number of times. Never got to the root cause. It is a quite complex machine. The status back then was that the CPU was running ok, but I never managed th TC02 to do more than wind the tape.

    I really should start working on it. But the PDP-8 core memory has higher priority. And since it is located 100 km away I can only work a bit from time to time. Maybe we could convince Anders to start with his machine. It at least sits in his garage. And now he finshed the Dectape dumping project, so it is time for another project, right Anders?

    To have two peripherals I expect you daisy chain that clumsy IO cables. Some kind of coaxial cables in it if I remember correctly. Do you have cables for connectong two devices?

  3. #3

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    Sounds interesting, look forward to update on the PDP-9. What size space do you currently have and how big is the new space? Look forward to some pictures!!!

  4. #4
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    Quote Originally Posted by maxfli View Post
    Sounds interesting, look forward to update on the PDP-9. What size space do you currently have and how big is the new space? Look forward to some pictures!!!
    The original lab space was about 800 sq/ft, and the new space is about 2x the original space. It looks like complete chaos right now after the move, so it will take a few weeks to get back to normal. We also have 5,000 sq/ft of warehouse space that looks like a scene out of Indiana Jones.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  5. #5
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    Quote Originally Posted by MattisLind View Post
    But it did work quite well at some point, didn't it? I remember some video clip that it read from mag tape.
    We did have it running for a long time, but I don't think that the warehouse environment helps the reliability.

    Quote Originally Posted by MattisLind View Post
    My experience with our PDP-9 is that it also was breaking down quite often. This was 20 years + back. I remember that I replaced the same transistor on a certain card a number of times. Never got to the root cause. It is a quite complex machine. The status back then was that the CPU was running ok, but I never managed the TC02 to do more than wind the tape.
    The PDP-8/I and the PDP-12 have been very reliable after the move to the Lab space. Hopefully the PDP-9 will like the new space. The people at ACONIT had one of their PDP-9s running from DECtape for quite a while, but it didn't survive the move to their new space.

    The PDP-8/I has a TC01, so we can use that to test most of the FlipChips from the TC02. Once we fix the CPU I think that we can get the TC02 to work.

    Quote Originally Posted by MattisLind View Post
    To have two peripherals I expect you daisy chain that clumsy IO cables. Some kind of coaxial cables in it if I remember correctly. Do you have cables for connecting two devices?
    We don't have any of the special PDP-9 I/O cables. We used 8x PDP-8 COAX cables to connect the TC59, and just received some more PDP-8 COAX I/O cables to connect the TC02. I think that we could use PDP-10 I/O cables in place of the PDP-9 I/O cables.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  6. #6
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    It was a little messy after the move, but now the PDP-9 has some nice company.
    DEC Equipment.jpg
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  7. #7

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    Cool looks like its coming together!!! What else do you have at the museum?

  8. #8
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    Quote Originally Posted by maxfli View Post
    Cool looks like its coming together!!! What else do you have at the museum?
    Just a few more systems; http://www.ricomputermuseum.org/Home/equipment
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  9. #9
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    Nicely put, Mike - I didn't know you did understatement! :>)

  10. #10

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    Quote Originally Posted by m_thompson View Post
    Cool you have some Cray systems, are they functional units?

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