NYC Resistor Gets A PDP-11/34

PDP-11/34 NYCR

[Trammel Hudson] and NYC Resistor have gotten their hands on some old computing iron in the form of a PDP-11/34.  The PDP-11 is a 16 bit minicomputer made by Digital Equipment Corporation (DEC). Various incarnations of the PDP-11 were sold from the 1970’s all the way into the 1990’s. NYC Resistor’s model is has a label dating it to 1983.

The PDP was found in an old storage unit in the Bronx. Moving several racks of equipment across the city is no small feat, but NYC Resistor members have it done it so many times they’ve got it down to a science.

Once power is applied, a stock PDP won’t actually do anything until the boot loader is keyed in from the CPU front panel. Thankfully this particular PDP-11 had its boot instructions printed on a label on the CPU. NYCR’s machine also includes an M9312 “bootstrap / Unibus terminator” board, which allows the machine to boot at the push of a button.

The team connected the racks, terminals, and drives. Carefully following the instructions, they actually got their PDP to boot up! Their next step is to start reading in some of the old tapes that came with the machine. We’re all waiting with bated breath to see what “digitized monkey brains” contains. Once the machine is fully functional, we hope they get it on the internet and load up The Hackaday Retro Edition.

40 thoughts on “NYC Resistor Gets A PDP-11/34

  1. Well, here come all the gray beards… I worked with a lot of DEC equipment, including the PDP 11/34. They typically ran RSX11 or some variety of Unix (System V). By today’s standards, they were short on memory and disk space. Magtapes, in hindsight, were never any fun beyond the similarity to blinky lights, it was fun to watch them spin. Being a pack rat, I’m sure I have some PDP hardware/software manuals I can donate.

  2. while this is kind of cool I doubt it will be of much use and will suck a hell of a lot of electricity. Is a makerspace a museum? Everything the real PDP-11 can do can be done under emulation with a thousandth of the power. Granted it won’t spin real tapes and blink real CPU panel lights but that sort of thing quickly gets to be more of a tech museum than hands-on-makerspace thing I’d think.

      1. Or adding a whisk to each tape reel post and parking it in the kitchen next to the fridge, it only whips pre-whipped cream though since you have to hold the bowl up to the whisks.

    1. Could always be a reminder to use concise and efficient code? One day people may look at something like this in the same way we look at the Rosetta Stone, though that’s your point about a museum piece rather than a functional tool.

    2. Nothing wrong with having some historical gear to pique people’s curiosity and inspire them. It isn’t like these things are exceedingly rare (yet), so no harm in some being in less than optimal conditions.

  3. Cool Find…

    Watch the mains feed. My experience with the PDP 11 series is that they were very sensitive to supply noise and would crash if the supply was noisy. I remember in the 70’s having to install a 250 pound isolation transformer to cure the problem.

    1. On a related note, Reed College’s PDP-11 apparently was finicky about sags in the mains power, so a student figured out a way to detect a fluctuation and basically hibernate the machine by writing the registers to the (non volatile) magnetic core memory before it was too late. He got it working under test conditions, but it never seemed to work for real world conditions. Or maybe it did. The guy who told me the story said he came back for a visit and the hibernation was apparently working, but he never got the story of who finished the hack, or how.

  4. A buddy of mine brought an 11/34 over once and we scrapped it for parts. I made a rack for my pickup truck out of some of the frame, and this cabinet for my garage out the rest, and gutted hard disk drives.

    Each one of those drawers is the case of an HDD. We had a lot of fun shattering the glass platters inside those HDDs too. Screw that old tech! heh It was when I stripped down my second minicomputer, an NEC, that I really had to step up my desoldering game. I mean you wouldn’t believe the size of the pile of circuit boards I got. You’re not going to sit there with a soldering iron and take them apart. Well, maybe you are, but I wasn’t about to.

    There are some great parts inside all of that old junk. I consider people who try to keep the whole units alive kind of dumb though. An Arduino probably has more power than one of those dinosaurs does.

      1. Enter my obsolete electronic chop shop MUWAHAHAHAHA! I love stripping commercial gear from that era. The Holy Grail though would be to strip a signed Apple 1, then burn the plywood base naked, dancing around the fire, by the light of the full Moon, or maybe a ring of Linux PCs. I would so totally do that. That would just be wanton destruction for the sake of destruction though. Because I hate Motorola CPUs, and Apple.

    1. An Arduino does have many times more computational power than the PDP11.

      However, that’s completely missing the point. The point is that it’s history. You wouldn’t be staring at your 1440×900 screen running off your 3.7GHz quad core processor with GBs of ram and TBs of HDD if not for the steps we went through with these minicomputers.

      It’s part of our past, it’s very important history, not only for computer science, but in literally every other field as well.

      1. Then put one in a museum. Better yet put a picture of one in a museum. Because the real thing takes up too much space. Then make more history with the scrap you can pull off of those old pigs.

        1. Sigh…. Wny not? Everyone knows that a picture of a machine is every bit as educational as the actual functioning machine. That is why no one ever goes to air shows or classic car shows.

          1. I love classic car shows, and I absolutely love seeing old hardware, working or not. There is something awesome about looking at a piece of tech and the people who would have been working on it or building it many many years ago.

  5. DEC a once great company. Many a joke about how many DEC engineers does it take to change a lightbulb ? I used to be a “field engineer” working on their systems and can attest to the heavy duty construction that went into the hardware.

    I also built a Heathkit H-11 computer (built off the KD11F – LSI-11 CPU card).

    As others have pointed out, the PDP-11/34 is now more of a museum artifact.
    However, in it’s day, it ran “mission critical” applications 24×7. I once recall having to take a process control system offline and the CEO of the company was furious. Since the machinery it controlled was non-productive, costing the firm hundreds of thousands of dollars a day in lost revenue.

  6. I should have mentioned one of my favorite stories regarding the PDP’s, their system bus was called the Unibus and like any interface, it had registers associated with it. This interface has a true FUBAR documented. It’s the Failed UniBus Address Register (seriously).

  7. My first experience writing assembly language was for this machine (via emulator). Now, a few years later I know what a great job they did on the instruction set. My university actually has NIB DEC parts and I am trying to get them before graduation, otherwise they will throw them out!

  8. So, a few years ago (1983 ish) I installed a PDP 11/73 in each of P-3s we had 6 terminals and two printers and a 5mb hard drive in briefcase to up load and down load the mission parameters and collected data. all of this is commonplace now but back then it was pretty cool stuff, for long flights we entertained ourselves with DND….

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