A low cost remake of the PDP-11/70

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This will be a low-cost remake of the PDP-11/70. It uses the same approach as my PiDP-8, using a modified simh on a Pi, hiding behind a replica 11/70 front panel.
This time, CAD design will be my learning curve; to reproduce the iconic PDP-11 in spirit the replica needs to have a case with the same slanted, white panel frame. Custom-made switches are also be part of the Maker Challenge. Can't do without.

Project planning: 100% open source hard/software
- test version (PCB + software) by the end of February
- CAD/molds done by May

For technical details, see my PiDP-8 project. In terms of electronics and software, the PiDP-11 is not much more than a variation of the PiDP-8's design.

The PiDP-11 will be a bit more costly to make, because of the planned custom case. Design goal is to stay well under $250 though. If done well, the molds for switches and case will be useful for other PDP-11 projects as well. The idea is to have them available as 'open-source molds'. If such a concept exists. :)

  • 1 × Raspberry Pi 2
  • 64 × 5mm LEDs, red 700nm+ Red, not 600nm.modern hue
  • 42 × Diodes 4148
  • 1 × UDN2981A Interface and IO ICs / Peripheral Drivers and Actuators
  • 30 × Standard switch bodies with custom switch caps normal C&K style switches could be used if cosmetics don't matter

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  • Case Progress

    Oscarv04/05/2017 at 13:53 2 comments

    It's been a good few months without an update. Real Life interfered, as it does. But also, I had lots of trouble getting the CAD design ready for injection molding. Stuff you don't think about: selecting brass inserts for screws, and how they should fit in the plastic. Controlling cost by ensuring a hobbyist can mount the inserts himself...

    Hopefully, a professional checkup on the CAD file means it is now good to go. One more 3D printed prototype to check these inserts, and then the case should be done.

    About time, the rest of the project was done 6 months ago. I'm curious if at the end of this I feel injection molding is just a horrible idea for hobbyists, or whether I just was slow climbing the learning curve. We'll see.

  • Case prototype arrives - PiDP-11 in its final shape

    Oscarv10/12/2016 at 18:32 0 comments

    Today was a great day - after 10 months, all the parts were fitted together for the first time. As a 3D printed prototype of the case just arrived.

    Excuse the bad photo quality, late at night again and I still have a low-tech camera that can't deal with dim lighting conditions. But actually, grainy pictures are a Good Thing because there's a lot of finer detail still to be done. The new case is just dropped over my prototype like a hood - not even screwed together yet.

    Still, a fiiiiine day for the project. The PiDP-11 will be pretty, now I know for sure :)

  • Switches! Lots of them...

    Oscarv09/12/2016 at 23:11 0 comments

    Well, it took months but today I got a batch of switches from the factory. Yay!

    That leaves the injection-molded case still to do... Hopefully more progress on that in two weeks' time :)

  • Colour matching - not as simple as you'd think

    Oscarv06/09/2016 at 22:35 3 comments

    The PDP-11 uses a very peculiar colour scheme. Getting the colours right is crucial to get that early '70s feeling across. Unfortunately, getting colour exactly right is much, much harder than you'd think. The problem starts with computer screens, which unless they are professionally calibrated do not show colours faithfully *at all*. Then, the manufacturer of my acrylic panels has the same problem, so I had to make a special acrylic bar with all possible colours to pick the right one.

    And now, I have to make sure the switch manufacturer delivers the exact right colour. Today I went to a local specialist shop, and identified the near-perfect Pantone colours for the switch manufacturer.

    That is, if anyone is ever interested, Pantone numbers 222 and 187. For fun or otherwise, below are colour sets I got off high-quality photos of the PDP-11. Even good cameras are off no matter what you do. Seriously, that is how far off you get without 'professional' colour calibration. It illustrates the misery of colour matching:

    I just hope the switch guys are precise with their colour matching. Otherwise, the test sample (minimum size 4000 switches!) will be a very expensive write-off :(

  • Test Samples of Replica Switches

    Oscarv05/23/2016 at 07:13 1 comment

    After 4 months of waiting, the pre-production samples of the switches came from the factory! Yay! They look exactly as I had intended, so that is a relief. Having to change the mold is an expensive thing to do. Now, all that's left is to ensure they are produced in the right colours - as is obvious from the picture, these samples are in black.

    Now, back to making a CAD design that works for the case...

  • Pondering Case Design...

    Oscarv05/06/2016 at 01:07 0 comments

    It will be horribly expensive to make, but this is the case for which I'll ask quotes from a few manufacturers, using different techniques. Just to see what's feasible:

  • Case Design

    Oscarv05/05/2016 at 00:11 0 comments

    It's been a month or so since my last post, but progress has been made. Samples of the replica switches will arrive on Friday. And thanks to Henk of, I started in earnest on case design. He let me borrow one of his original bezels/frames - thank you, I'll be careful with it!

    It would have been impossible, with hindsight, to exactly replicate the bezel without having the real one at my desk.

    I started the CAD work yesterday, and followed the path of least resistance by doing it in Sketchup. Which, maybe, will not be the best idea in the end but I will see. At least I've got all the measurements done for a mostly-finished v0.1 version:

    Next version should be good enough to go to a plastics manufacturer for evaluation and testing. Hopefully in the next two weeks, as I visited two of them recently to learn more about the whole process.

  • Progress: Got To Blinky!

    Oscarv03/24/2016 at 00:02 1 comment

    A blinkenlight movie means progress. Not there yet, but here's the PiDP-11 doing the '11's signature pattern:

    To be continued. As in, tomorrow night.

  • Prototype #1...

    Oscarv03/19/2016 at 20:24 0 comments

    Not in the right case, not with the right switches, with an imperfect acrylic panel and most certainly not in the right colours. But it seems to work with initial tests...

    Magically, the encoder switches turned up this morning just when I needed them. So they are in! Tomorrow I'll start adapting the BlinkenBone server. Five days left before I leave for VCF SE.

  • PCB came in. So did the flu...

    Oscarv03/18/2016 at 22:08 0 comments after four days, I've only just got the PCB finished. But testing will have to wait till tomorrow. Still, it's (almost) all there: the temporary switches painted to match the panel, the PCB... now it'll be a matter of putting it all in its case, and focusing on the software. Oh - and the rotary encoders are still missing. Two months shipping time is not enough?

    Again, the final form factor will be different. Different case, different switches. But this prototype will help me drive the bugs out.

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Kevin Szabo wrote 01/25/2018 at 18:44 point

Will the final PiDP-11 console be the exact dimensions of the real PDP-11/70, or slightly smaller?  One reason i ask is that I have a physical PDP-11/70 front panel but it is lacking the white bezel that you are getting injection-molded.  If this bezel is close to the original dimensions then I can hopefully purchase one from you and upgrade my 11/70 panel :-)  And I would probably buy a full PiDP-11/70 kit anyway because it is so cool.

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Carl wrote 07/16/2017 at 13:18 point

Saw the PDP--8 project and, while reading, thought, "Man, I really would love to have a PDP-11 sitting on the bookshelf!" and then...  Thank you for all of the work you put into the details. Signed up with hackaday to follow and looking forward to the release!

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hackerday wrote 05/19/2016 at 20:12 point

Saw this at VFCe in Munich. Love it! Tell me when it's available, please.

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andy wrote 04/04/2016 at 01:46 point

Oscar- I would love to sign up for your PiDP-11 Early Adopter Program :-)...very excited about this project ... oh and thanks for the 2x PiDP8s by the way, one is assembled and working, the other will be a gift that I will surely assemble more quickly than the first one!  best wishes, Andy

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S.Edwards wrote 03/05/2016 at 01:11 point

Let me know as soon as you have a kit or an assembled product for sale.  I will buy at least one of them.  It was with a pdp11/70 that I learned Unix back in the 1970s.

pdp11/70 trivia: the unlabeled toggle switch (to the right of bit zero) is the secret "lamp test".  It is unlabeled because it was thought that LEDs, unlike the incandescent bulbs in earlier pdp models, would never fail.  When activated, all of the LEDs are lit.

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Andrew Wasson wrote 12/06/2015 at 01:40 point

Looking forward to this one. My PiPDP-8 went together extremely well and is happily blinking away. The PDP-11/70 front panel and switches sure is a thing of beauty. 

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Oscarv wrote 10/14/2015 at 19:53 point

Thanks! This one will hopefully teach me much more about manufacturing, CAD, and whatnot. Whole new world... Electronically, it's the same trick as the PiDP-8. 

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Benchoff wrote 10/14/2015 at 19:47 point

It begins! Can't wait to see it finished

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