The 1975 PDP-11/70 was the first computer with unix and C. But there is much more to make this an interesting minicomputer playground.
The PiDP-11 uses a modified simh on a Pi, hiding behind a replica front panel. It runs everything: From Unix v5 to 2.11BSD to RSX-11, multi-user, vector graphics and all. CAD design and injection molding were new territory for me; I felt that a replica had to the exact same slanted, white panel frame to reproduce the original's spirit.
Project completed. The kit is now at obsolescence.wixsite.com/obsolescence/pidp-11 We're still adding to the machine's built-in "software museum", join the PiDP-11 Google Group for more!
Details
In terms of electronics and software, the PiDP-11 is similar to my PiDP-8. The PiDP-11 turned out more costly to make, because of the custom case (injection molding!). I hit the upper limit of the design goal: to stay under $250.
The molds for switches and case will hopefully be useful for other PDP-11 projects as well. The idea is to have these parts available as 'open-source molds'. If such a concept exists. :)
(update - in fact, a plug-in FPGA board for the PiDP-11 is being worked on as part of the PDP2011 project, in case simh on a Pi does not meet your needs).
Components
1×
Raspberry Pi +/2/3/3+
64×
5mm LEDs, red
37×
Diodes 4148
1×
UDN2981A or equivalent
Interface and IO ICs / Peripheral Drivers and Actuators
Rene Richarz just released an animated TU-56 DECTape unit for the PiDP-11. In the form of a rack-mounted HDMI display. Much time was spent thinking of how to replicate a DECtape unit for the PiDP-11, but Rene did what makes most sense: have a high-fidelity DECtape animation instead, on a low-cost HDMI screen.
DECtape was crucial in the early days of DEC, and having a timing-exact virtual unit gives a pretty realistic experience of life before floppy disks:
Thank you, Rene! Apparently, a TU-77 magtape unit is forthcoming. It's a good thing that the new Raspberry Pi 4 has two HDMI outputs.
The past couple of weeks have seen some interesting developments on the ancient unix side of the PDP-11. We have the high-resolution Tektronix vector display with loads of software and C library of course, the http daemon (running on just simulated 1970s hardware, mind you!) has been boosted with CGI, and quite a few other patches and goodies have been worked on (even the Ingres database has been brought to life).
Here is the thread with the latest disk image download: (link)
I just updated the firmware to support the new Pi 4, which has a slightly different way of enabling the internal pull-up resistors on the GPIO.
So... where the Pi 3B+ was 6 times faster than the real 11/70 at 7241 dhrystones/second, versus 1250 for the 1975 original... you can now enjoy a 12x speed boost versus 1975. For those who like to be as authentic as possible, use a Pi 2! Or use the 'set throttle' configuration to slow down the Pi 4. Or run multiple 11/70s in parallel. At least the Pi 4 shows there's still progress in computing and 2.11BSD unix feels like lightning :)
The other nice thing of the Pi 4 is that you can use one HDMI display for a faithful CRT display (using cool-retro-term) and a second one for the very cool Tektronixvector tube simulation, which really uses the 4K resolution of the Pi 4:
Beige-O-Vision just made a very nice 4-part Youtube movie showing how to build the PiDP-11. Worth mentioning here, as it surely will save builders a lot of time. Since nobody reads written Building Instructions anymore these days...
[Rene] wrote a very pretty emulator for the Tektronix 4010 vector graphics display. And got everything set up inside 2.11BSD so you can actually use it. It's a great step forward: not only can the PiDP-11 now do vector graphics on BSD, but the C libraries are included as well! It turns out that making cool graphics takes only a tiny bit of C...
We already had BSD unix networked on the PiDP-11, so this is becoming a pretty top-of-the line scientific minicomputing setup ;)
One of the next challenges is to get uucp going on Unix v7, as a bridge between the Pi and the PDP-11 sides of the PiDP-11... nontrivial.
The new software (and software museum) distribution is currently in beta stage. Use your PiDP-11 with RSX-11 as a web server, surf the internet with 2.11BSD, play lunar lander on a simulated vector display, follow the Lions Commentary on a real Unix v6... things are developing rapidly at the moment.
That is also why the manual is in .odt format. It's being added to constantly. Best opened in MS Word, but LibreOffice on the Pi is OK too. Have a look:
First comes a software update with polished-up boot disk images for unix v5, v6, v7, 2.11 BSD and Ultrix, hopefully next week. Got to do it before January 1st, Unix's 50th birthday!
Then, Jörg has released the UniBone card. This thing lets Linux drive the old Unibus directly. It is possible to have a software CPU simulation run inside an old, potentially dead, PDP-11 and let it use its real core memory as well as any real PDP-11 disks... this needs hooking up to the PiDP :)
Lastly, many thanks to PJ Evans for publishing this article in the latest MagPi edition! Hopefully that gets new people sucked into the dark world of PDP-11 computing.
(note - MagPi is a truly Open Source publication, Creative Commons (BY-SA-NC 3.0))
Well, today was a great day - the day that the 600th PiDP-11 saw the light of day! I'll celebrate this weekend at the Vintage Computer Festival Zürich (vcfe.ch, that's a shameless plug...)
But there are hardware developments too. Soon, we'll have the PDP2011, Sytse's FPGA version of the PDP-11, as a plug-in module. So you can choose whether you like a Raspberry Pi simulating inside, or a FPGA hardware version to blink the front panel.
And Jörg is cranking out the first production UniBones - a reasonably mad device that can plug in to a real DEC Unibus. Either to emulate any storage peripheral for a real PDP-11, or to hook up any real PDP-11 hardware onto the simh running inside the PiDP-11. Yes, you will be able to connect an RK-05 to the PiDP-11... who'd have thought that two years ago!
Here, somewhere at the end of the last row, is PiDP-11 #600 waiting for the postman. One more grainy late-night picture:
Ouch - the last update here was almost a year ago to the day.
As it turns out, injection molding is not for noobs. Many thanks for all the help I got from here, including the massively helpful final check before the mold was made. It only took me 350 revisions of the CAD model, and 30 more from others... And it took custom-made brass inserts to hold the bolts in the case. So Iearned a lot, but it can be summarised: if you consider injection molding for a hobby, don't.
But! The first 20 PiDP-11 kits went out to beta testers, and other than a slightly too-short hex spacer, no problems during the final shake-out! So here it is, the brand-new PiDP-11/70:
Over the last few weeks, I've made a web site for the kit, and a Google Group is live as well. Now, the focus shifts to polishing up the (currently pre-alpha) software, and kits will go out from next month. Here are the kit contents:
Stupidly I forgot to put the back panel of the case in the picture, but it's on my site anyway. That back panel taught me about laser cutting (press-out slots for connectors etc), and after injection molding, that is the way to go for any following project. Easy, low-cost and very precise results.
I'll post some more updates in the coming weeks. As the PiDP-11 is a simhBlinkenBone device, I just wrapped up a virtual PiDP-11 with Jörg's virtual 11/70 front panel. That'll add to the fun as we go about building a right proper PDP-11 Software Museum into the software. From RT-11 to Unix v5/6/7 via Ultrix to 2.11BSD to RSX-11M Plus with networking, it should all be there of course!
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.
Hi Oscar, my dad put his together (in about an afternoon, which tells you how excited he was to get it!), and he absolutely loves it. Thanks for making this kit! best wishes -- Peter
Nice work. Takes me back. The first Unix I used was on a PDP11/45. Strictly speaking one did not buy Unix as one would software these days. Software as a packaged product was in the future then. Rather institutions, academic mostly, purchased a license from Bell Labs to use it. Tapes came with source code and institutions made modifications so conferences started where programmers talked about what they did with Unix. Mostly to support teaching, but there were research uses. The beginnings of software code sharing.
It was only later that AT&T developed commercial versions.
Hi Oscar, I am working on a TTL CPU with PDP11 instruction set. It would be great to connect it to your nice front panel ! My project can be found here: #Kobold retro TTL computer
Roel, yes - I follow your project of course! If you want to use the PiDP as its front panel, you have one problem to overcome: the LED display is multiplexed. The simplest solution would be to sample your address & data lines with a microcontroller, which then sends the status of the lines through to the front panel.
Alternatively, just make a new PCB for inside the PiDP (keep the same PCB layout, just change the wiring, not too hard). Let me know if I can help. Regards, Oscar.
Oscar! I was actually wondering about the PiDP-11 a few days ago. I have a pair of J-11 processors and a few Russian clones from planning on participating in the PDPII project. What's the usable dimensions inside the case if a board was mounted on the back with about 1cm standoff? I can barely find time for personal projects, but I want to do a PDP-11 build with expansion so will add a port to the back, or have a new casing made that will fit the front panel and board.
The back panel (which fits exactly in the case) is 313.5mm by 171.5mm. I can mail you the drawings if you want. You could mount a PCB behind it easily, flush to the panel. The guy behind the PDP2011 (FPGA version) is doing that; there is enough space for a PCB plus parts on the front; and the connectors mounted on the back of the PCB so they come out of the back panel. It would be amazing to fit a real J-11 board...
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.
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!
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
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.
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.
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.
Oscarv
Dylan Radcliffe
James
Hi Oscar, my dad put his together (in about an afternoon, which tells you how excited he was to get it!), and he absolutely loves it. Thanks for making this kit! best wishes -- Peter