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Digital Hardware Hacking Hardware Build

Rebuilding the PDP-11/70 with a Raspberry Pi ( 96

"You could look at this as a smallish PDP-11/70, built with modern parts," Oscar Vermeulen writes on his site. "Or alternatively, and equally valid, as a fancy front panel case for a Raspberry Pi."

Long-time Slashdot reader cptnapalm writes: Oscar Vermeulen's PiDP-11 front panel, modeling a PDP-11/70 in all its colorful glory, has been released to beta testers. This is Mr. Vermeulen's second DEC front panel; his PiDP-8 was released a few years ago. The PiDP-11 panel is designed to work with a Raspberry Pi running simh or, possibly, a FPGA implementation of the Digital Equipment Corporation PDP-11... In addition to the front panel with its switches and blinkenlights, also included is a prototyping area for the possibility of adding new hardware...

UNIX and later BSD were developed on the PDP-11, including both the creation of the C language, the pipe concept and the text editor vi.

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Rebuilding the PDP-11/70 with a Raspberry Pi

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  • Pi does it all (Score:5, Insightful)

    by amiga3D ( 567632 ) on Saturday May 19, 2018 @12:38PM (#56638838)

    I'm always amazed at what people use a Pi for. While bad mouthed for it's limitations it seems the Swiss Knife of tiny SBC devices.

    • by Anonymous Coward

      People who badmouth the Pi for its limitations are not the ones that are interesting.

      The interesting people look at the limitations of the Pi (especially the single core variants) and say 'Challenge accepted'. Then they sit down and make it do things the people above didn't think possible.

    • Re:Pi does it all (Score:4, Interesting)

      by mystik ( 38627 ) on Saturday May 19, 2018 @01:31PM (#56639018) Homepage Journal

      Before the Pi, you'd see all sorts of devices hacked to get new firmwares and new capabilities into them, that the original creator hadn't even dreamed of. Remember the Chumby? Hacking various routers?

      The Pi platform lets you skip that sometimes difficult hacking phase, and onto the, "What could I do with this hardware?!"

      • by amiga3D ( 567632 )

        I think you are right. A lot of very creative people now are free to just use the hardware without having to fight against the deliberate crippling of the hardware by it's creators. You'd see someone hack the Playstation to get it to do cool stuff and then a firmware update would wipe that out.

        • You'd see someone hack the Playstation to get it to do cool stuff and then a firmware update would wipe that out.

          Well sure, if you were dumb enough to accept the firmware update instead of sideloading API updates designed to force you to for a friend.

          It's sort of cool that they made this but I refuse to accept a PDP-11 that doesn't contain disc packs, tape drives and green screen terminals. It just doesn't seem right. Unlike screwing Sony in the wake of that massive rootkit scan []

          • Where I work the IBM tape library was 'automated' decades ago. It is used exactly the same way, but it is, of course, all DASD drive now. And that's virtualized in a SAN inside a VM cluster that merely mimics a tape library.

            I use PuTTY daily. At work it's HostExplorer, they can jam PComm up their Java. Lots of VT100 emulations out there.

            Needless to say a PiDP-11 would handle mSATA fine. Imagine giving your VMS install more data space than existed in the world when it was introduced.

            First-world problems. Wit

          • DECwriter II terminals are also acceptable.
          • Please, Please, can someone 3D print a TU56 emulation to the same scale!

            I don't care if it uses standard 1/2" tape, and the data is actually on SD cards, but it should look like its on DECtape.

            A paper tape reader/punch to scale, but with full size paper tape might be nice, but I am not sure you could get paper tape for it anyway.

    • I'm always amazed at what people use a Pi for.

      An IBM mainframe emulator on a Pi would be really impressive . . . impressive, but probably not very useful. And there is probably a butt-ugly rat tail of legal issues.

      Now, Linux on Z is supposedly Open Source . . . so that could be possible legally . . . but again, probably not very useful.

      • My brother runs a serious shop that still uses RPG. SO go ahead, either a S/3 or S/38, that code is still running businesses. And yes, IBM would probably be a hassle, but then again that old S/3 code is still running on Zseries emulating AS/400-S/3x-S/3...

        • by dwywit ( 1109409 )

          I'll reserve my applause for the person/s who manage to emulate OS400/IBM i on RPi or x86/64.

          • Do you want OS/400 or CL & RPG?

            • by dwywit ( 1109409 )

              Well, OS400 and CL. I like the way OS400 manages resources - the subsystems, memory pools, routing classes, etc.

              I also like the ability to compile CL.

              But I'll take RPG if I have to ;-)

              • ToolSet, Java, and C are all available in the OS/400 constellation. COBOL for the brave. The Java implementation has a robust GUI toolkit, but mostly intended to support terminals, though it will leverage your Windows machines well, and there are mobile and Web toolkits available, which my brother has used to offer a strong anywhere/anytime support structure for real-time global manufacturing support for a DOD contractor/manufacturer who also supports virtually all the aircraft industry in civilian efforts.

                • by dwywit ( 1109409 )

                  One of my early jobs was porting accounting programs written in System/36 BASIC to the AS/400. That brings back some eye-twitching memories.

                  BASIC on the /36 was interpreted IIRC. Then it was introduced to the two-level microcode world of the AS/400, and to their credit, IBM's emulated /36 mode on the AS/400 made it all work smoothly.

                  Sometimes IBM gets it right

                  • The S/32 was based on the S/3, and ran S/3 code unmodified, right through the S/38. AS/400 ran S/38 emulated, and I think had a dedicated S/36 emulation, as many users didn't want to leave S/36, a really good version of the hardware and software. Of course AS/400 changed a lot and was worth adopting native, and I think I-Series took you as far as you could go with Application Systems, even supporting Linux. I know my brother still has lots of RPG code running, just behind Java UI and mobile shells.

                • by dwywit ( 1109409 )

                  These days I can scratch my AS/400 itch at

                  It's back online after some users abused the T&Cs.

                  • by wwphx ( 225607 )
                    Thanks for the link. A prev job had an old 400 and I really enjoyed working on it and would enjoy playing on one again. Pity some people thought they could make a quick buck off it.
      • by rnturn ( 11092 )

        An IBM mainframe emulator on a Pi would be really impressive . . .

        Pi/CMS? That would be pretty cool to see pulled off.

      • The Hercules emulator [] will emulate an IBM z system on your PC. Now, any IBM mainframe software that's not decades old is copyright and basically impossible for an ordinary Joe to get for an emulator. But in the 60s and 70s, IBM released much of their system software free, figuring to make money on the hardware. You can get an MVS turnkey system [] for Hercules built with the last free version of MVS (3.8j). You get an assembler (G--H and HLASM were licensed program products) and TSO (not ISPF or SDSF, thou

    • I don't get it though. We've had the SimhH simulator for about 25 years now, just putting it on a Raspberry Pi is trivial, so the only "story" here is the front panel. Ie, copy source code onto the RPi, run make, and you're done, because the Raspberry Pi is a relatively high powered computer. You can find PDP 11 like computers built by hand - that is, the logic built by hand from TTL gates or relays, those are certainly much more interesting stories. Follow the homebrew cpu ring [].

      Granted, this is fun to p

  • by Entrope ( 68843 ) on Saturday May 19, 2018 @01:03PM (#56638930) Homepage

    ed. Not vi, ed.

    Now get off my lawn, I'm growing belt onions right there.

    • Well I just use cat. I am lazy

      • ED was first, line editing only, then we had EDT (1978?). I remember seeing that for the first time and having my mind blown away...

        • Cat was around even earlier. Bahoo you younglings. I do not need features and use pipe when cat displays too much info in a terminal

    • Real programmers use emacs. Or butterflies...
    • by Waffle Iron ( 339739 ) on Saturday May 19, 2018 @01:56PM (#56639140)

      Software text editors are for wannabe hipsters.

      Serious developers use the switches and LEDs that are right there on the front panel. Why would you pay for all that hardware if you didn't intend to use it?

    • by Xtifr ( 1323 )

      For those who missed the joke: ed is the standard text editor [].

    • ed - for when you're using a teletype terminal.
  • by lenski ( 96498 ) on Saturday May 19, 2018 @01:14PM (#56638968)

    The builder set up a prototyping area, and my thought would be to install an audio amp and speakers to replicate the 12 (? it's been 40 years for me...) fans it needed for cooling. To say nothing of the RK-05. Of course an organization that could afford a /70 could probably afford the RP06 drives to go with it.

    I remember wishing that someday if I could get really rich, I could someday have an 11/45.

    ..This comment was typed on a 2016-vintage Intel NUC with 16 gig RAM, 1 TB NVMe SSD and a 40-inch 4k monitor. Total "investment": $1500, having splurged on the entirely unnecessary NVMe... Nothing fancy but so many orders of magnitude more powerful than the 11/70 that the systems are incomparable.

    • by Xtifr ( 1323 )

      The really tricky part is getting the Pi to emulate the thermal output of the original. I had a friend who had an old 11/70 set up in his bedroom. He only powered it up during winter, when he wanted the extra heat in any case. :)

      • by rnturn ( 11092 )
        He must have had some excellent earplugs to block out the noise of an 11/70. We had one that had been stripped down to the bare essentials--no memory enclosures; Setasi static RAM board in the CPU backplane instead; no removable pack drives; Dilog controller running Fujitsu 5.25in SCSI disks--and even then I really couldn't stand to be in the same room as that beast for more than a few minutes. I can't imagine anyone being able to sleep in the same room as one.
        • Also? Three-phase power.
          We had a beast in a friends garage, in the early 90's. He needed to convince his wife to have the new run from the panel mains.

          That was that last time I touched one of these, with a crappy Wyse 50 terminal, instead of the Honeywell Teleypes or Lear Seigler ADM-3 terminals we had in the labs, where I first used Unix and Berkeley extensions.

        • by Xtifr ( 1323 )

          He didn't sleep with it running--that would be silly and pointless. (There are far more efficient ways to generate heat.) He just didn't power it up when the heat would have been intolerable--so, only during winter.

          It was definitely loud, but I certainly didn't think it was unbearable. At least, not when you were awake and playing with it.

          (His also hadn't been stripped down, so the outer casing may have helped reduce the noise--I'm really not sure. It's the only one I've ever been in the same room with.)


      • Put an Antminer in the case for authenticity.

  • I miss those days, cut my baby teeth on a PDP 11/70 with RSX11M+ OS. Did Fortran 66, Fortran 77, Assembler and C code on them.
    We also had 11/34s and a really small one in the lab with a low serial number. It came with the pizza box drives and paper-tape reader/writers.

    • PDP 11/70? Eee, tha' were lucky. I cut my computer teeth on the PDP 8/E. I also did the maintenance course on it, which with my electronics degree meant I could follow a high-level instruction (in FOCAL) all the way down to the movement of electrons in specific gates. Am I of the last generation for whom such an end-to-end view of computing was reasonably commonplace?

      • by lenski ( 96498 )

        Luxury... PDP-8/L, paper tape only and no disk. (Well, several months later, we got an RK05. 2.3 million words... It was huge and lightning fast.)

        I still remember the wonderment upon first learning of the -11 and its stack. Reentrant code!

        I still have the first programmed output of the decaying sine from the FOCAL example, glued to the inside cover of my CRC math tables book. It's a bit faded but still visible.

    • In 79-82, we had the cake-lid drives, that resembled a top-load washer. I have no idea of the sizes, I'm guessing they were 20 MB? Different disc-pacs for our use, and that on the weekends, when the school district did processing.

      We kept our personal files on 8" floppy disks, with a drive accessible in the common area of the lab, away from where the DEC and large peripherals were locked.

      There are several stories from this school. One is that the exchange student we had, Marcus Hess, went on to Cuckoo's Egg

    • Was that "really small one" a PDP-11/05?
  • Memories (Score:4, Interesting)

    by RhettLivingston ( 544140 ) on Saturday May 19, 2018 @01:57PM (#56639150) Journal
    The highlight of my Digital Electronics II Lab course in college was to design and prototype a PDP5 using 74xx series logic chips on breadboards. In comparison, the PDP 11/70 was an advanced supercomputer, but the task of designing even the simplest computer at the gate level really created an appreciation for the complexity of processors. It took 20 breadboards to prototype and worked for just a few minutes before a chip lost its smoke somewhere. Fun days!
  • fun game: Name DEC pdp11 OS by running idle light pattern...
    RT11, RSTS/E, RSX11 all had different light patterns.

    • by guygo ( 894298 )
      I remember that. I was in charge of an early cluster consisting of an 11/34, and 11/44, and an 11/70. The 44 had RSTS for a while, but we eventually went over to RSX-11M like the other 2. Teco anybody? DECNet? Hard drives the size of washing machines?
    • by rnturn ( 11092 )
      Not sure about the others, but on RSX you could substitute in your own light pattern. Simple matter of programming.
  • Oh God, please not the PDP--11/70 series!!!! (I forget, was that the one you had to boot up with paper tape????) Now, the older Perkin/Elmer super-minis were sweet!
    • by rnturn ( 11092 )
      You could but I never encountered one that required booting from paper tape. We had one that, for some reason, came with what I was told by a DEC field service tech was a complete set of the XXDP+ diagnostics on paper tape. Not sure who made the original purchase but they forgot to include the paper tape reader.
      • We booted from disc, in 79. You needed to toggle boot register on the front of the panel, tho. So not much different than tape. Students rarely got to do this, tho' I got some privileges for the locked room with this stuff and had the 3-ring runbook, to do this some mornings.

  • To get the full 32-bit experience
    • by ka9dgx ( 72702 )

      I was always in awe of the POLYD instruction - "Evaluate Polynomial, Double Precision"

  • I'm pleasantly surprised they tagged this correctly. Of course, the Digital Equipment Corporation [] hadn't exactly been lighting up the news, since they've been toast for nearly 20 years :-) Kudos for remembering them!

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