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back to article Nuke plants to rely on PDP-11 code UNTIL 2050!

The venerable PDP-11 minicomputer is still spry to this day, powering GE nuclear power-plant robots - and will do so for another 37 years. That's right: PDP-11 assembler coders are hard to find, but the nuclear industry is planning on keeping the 16-bit machines ticking over until 2050 – long enough for a couple of generations …

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  1. Bubba Von Braun
    Coffee/keyboard

    Ah those were the days..

    Yes, I still have a VM running RT-11/TSX Plus more for curiousity these days. As far as languages cant go past the venerable DIBOL a bastard cross between Basic/Fortran and Cobol. :-)

    Loved DCL on VMS, back where 2400ft tapes were new and 450mb drives to 16 hours to backup.

    Now are my MACRO-11 skills up to scratch.. hmm

    Also the OS lineage for DEC went TOPS - TSS - RT-11 - RSTS/E - RSX and VMS

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    1. Michael H.F. Wilkinson Silver badge
      Reply Icon
      Joke

      Re: Ah those were the days..

      DIBOL, short for DIABOLIC ?

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    2. John Sager
      Reply Icon

      Re: Ah those were the days..

      I wrote comms software for RSX-11S, including a device driver, back in the 80s. That whole structured overlay concept in RSX-11M to be able to run bigger programs was fairly mind-boggling. Luckily I never had to get to grips with it in anger. Thank <deity> for VM these days. I learned a lot about embedded software and general software design on that job.

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    3. Anonymous Coward
      Reply Icon
      Facepalm

      Re: Ah those were the days..

      "Also the OS lineage for DEC went TOPS - TSS - RT-11 - RSTS/E - RSX and VMS"

      Well, I can agree that these were all DEC operating systems, but they never ran on the same hardware architectures.

      TSS/RT11/RSTS/E and the IAS/RSX families (and various flavours of UNIX as noted by others) all ran on the 16-bit PDP-11 systems, VAX/VMS ran on the 32-bit VAX family in its first incarnation (later Alpha and subsequently IA64 as OpenVMS) .

      The TOPS family was of course a very different world of 36-bit systems ... but I'm sure that I have mentioned that before in other posts (!)

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  2. Steve Davies 3 Silver badge
    FAIL

    Pah

    Quote

    while VMS was born of the multiuser version of PDP.

    Ths seems to imply that PDP-11 systems were not multi-user.

    This is so far from the truth that it really shames me the level to which accuracy of the El-Reg hacks has sunk to in revcent weeks.

    Can't you get anything right? A few google searched would have told you the real facts.

    The PDP-11 range of computers was sold with a number of different operating systems

    RT-11

    RSTS/E

    RSX-11M/M-Plus

    and a few older ones such as DOS.

    RSTS/E & RSX-11M/M-Plus were most certainly multi-user operating systems.

    One RSX-11/M-Plus customer had 128 users logged in to one PDP-11/70 with 256KWords on memory doing Transaction Processing (as we used to call it in them far off distant days)

    Yes, I worked for DEC (20 years).

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    1. Peter Gathercole Silver badge
      Reply Icon

      Re: Pah

      I was going to say exactly the same.

      And you've missed out UNIX, which was definitely multuser on the PDP-11.

      I think the hack was confusing PDP with RSX-11M Plus, which really is the ancestor of VMS.

      I was the primary technical support for RSX-11M on a SYSTIME 5000E (actually a PDP11/34e with 22-bit addressing and 2MB of memory - a strange beast) between 1982 and 1986. We had 12 terminals working relatively well on a system that on paper was little more powerful than a PC/AT.

      I think I can still do PDP-11 assembler. At one time, I used to be able to decode PDP-11 machine code in my head, although this was mainly because the instruction set was extremely regular. I still would recommend people looking at the instruction set to see how to design one. It's a classic.

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      1. Herbert Meyer
        Reply Icon
        Go

        Re: Pah

        The instruction set and runtime libs are forever preserved as "C" language and the std C runtime library. Don't tell me that "C" is a high level language. It depends what level of abstraction you want to (or know how to) write at.

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    2. david wilson
      Reply Icon

      Re: Pah

      >>"Quote"

      >> >>"while VMS was born of the multiuser version of PDP."

      >>"This seems to imply that PDP-11 systems were not multi-user."

      To me it would imply that there were multiuser PDP OSs for VMS to be some kind of successor to, though 'the multiuser version of PDP' does look like a poor choice of words, or a mistake in writing/editing.

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      1. PhilBuk
        Reply Icon

        Re: Pah

        Richard Chirgwin confuses things by using PDP to refer to the hardware and the OS. So, yes, a poor choice of words.

        Phil.

        (ex RT-11, RSTS/E, VMS - a long time ago)

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    3. robin48gx
      Reply Icon
      Happy

      Re: Pah

      I used to use a PDP-11/73, and it was multi-user unix, there were about ten people using it most of the time, working on C or with a Z80 cross compiler. vi was in use, a fantastic leap ahead from ed.

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  3. MacroRodent
    Mushroom

    Even analogue still used

    A recent article in the Finnish newspaper Helsingin Sanomat talked about the Olkiluoto nuclear plant (under construction), which will be controlled digitally, but this will also have an analogue back-up system at the insistence of the Finnish regulatory agency (STUK).

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    1. Richard Ball
      Reply Icon

      Re: Even analogue still used

      Hurrah for the 741!

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    2. Phil Endecott
      Reply Icon

      Re: Even analogue still used

      > controlled digitally, but this will also have an analogue back-up system

      My understanding is that they require N independent control systems that have no possibilities of common failure modes. So they might implement one using digital electronics, one using analogue electronics, and one using hydraulics. This isn't directly because those other systems are "old", but simply because they are "different".

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      1. Anonymous Coward
        Reply Icon
        Anonymous Coward

        Re: Even analogue still used

        "My understanding is that they require N independent control systems that have no possibilities of common failure modes."

        That was the pan-European regulatory stance for many years. The contractors at Olkiluoto didn't like that approach and wanted a variety of shared resources, shared sensors, etc (which obviously introduce the possibility of common failure modes).

        Don't know what is currently being proposed at Olkiluoto, or what the current regulatory stance is.

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        1. Tomato42
          Reply Icon
          Boffin

          Re: Even analogue still used

          @AC 16:33

          >The contractors at Olkiluoto didn't like that approach and wanted a variety

          > of shared resources, shared sensors, etc (which obviously introduce the

          > possibility of common failure modes).

          I got goosebumps after reading that.

          I think somebody needs their engineering licence revoked.

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  4. jake Silver badge

    I've been making money from my knowledge of the PDP11 family since 1979.

    I don't expect this to change any time soon.

    Shit that works, works. For some reason, kiddies fail to understand that simple concept.

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    1. jake Silver badge
      Reply Icon

      Re: I've been making money from my knowledge of the PDP11 family since 1979.

      Oh, look! My boo-bird is tweeting. How cute :-)

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      1. Anonymous Coward
        Reply Icon
        Anonymous Coward

        Re: I've been making money from my knowledge of the PDP11 family since 1979.

        Have another one for being sad enough to comment about being downvoted. Don't like not being held in awe, do you, jake?

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        1. jake Silver badge
          Reply Icon

          Re: I've been making money from my knowledge of the PDP11 family since 1979.

          Have issues, AC? Look within.

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          1. Anonymous Coward
            Reply Icon
            Anonymous Coward

            Re: I've been making money from my knowledge of the PDP11 family since 1979.

            It's clear from your constant peacocking behaviour, Jake, that you have several issues of your own...

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    2. asdf
      Reply Icon

      Re: I've been making money from my knowledge of the PDP11 family since 1979.

      >Shit that works, works.

      Yes and I am sure the guy that loved vacuum tubes and core memory said the same thing the generation before (or mercury tube memory the generation before that although that wasn't reliable at all). At some point it no longer is economical to build old shit. Yes you can even keep your 1950's Chevy's running for 60 years like Cuba if you have to, but that is not always the best long term plan.

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      1. Maverick
        Reply Icon
        Thumb Down

        Re: I've been making money from my knowledge of the PDP11 family since 1979.

        @asdf

        < Yes and I am sure the guy that loved vacuum tubes and core memory said the same thing the generation before >

        have a look on ebay at 2nd hand valve hifi amps, however if you want a quality one I hope you expect a large bonus this year !

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  5. naive

    Good choice, if there is one well defined machine architecture, then it is the PDP11.

    The people who designed this system should have been rewarded with an award.

    Programming it, is like programming K&R C. The world may feel safe with nuclear power plants controlled by such precise programming.

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    1. Anonymous Coward
      Reply Icon
      Anonymous Coward

      Re: if there is one well defined machine architecture, then it is the PDP11.

      True, but there were still enough oddities (and DEC documentation was still good enough quality) for various issues of the PDP11 Processor Handbooks to have appendices detailing differences between the various implementations. They weren't the kind of thing any normal programmer would ever encounter.

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      1. Primus Secundus Tertius
        Reply Icon

        Re: if there is one well defined machine architecture, then it is the PDP11.

        With variations.

        They removed the odd-address trap from the PDP11/23. That was a microprocessor architecture, and I guess they ran out of logic gates and had to trim something. Meant that kind of program bug was not immediately detected.

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    2. Chika
      Reply Icon
      Thumb Up

      I suppose that's one reason why I liked the PDP11. Just when you thought it couldn't go any further, there it was again in a new place doing its thing. I honestly didn't expect that something like this would happen again after all these years away, but it's a sign of exactly what good design can do for you.

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      1. Stoneshop
        Reply Icon
        Mushroom

        . Just when you thought it couldn't go any further, there it was again in a new place doing its thing

        Down in boreholes in Arizona, together with a Device Under Test: a nuclear bomb. Connected to another one topside, equipped with core memory. Even if that one was not expected to survive being tossed about, they could still try and read out the data in memory in another system.

        Being asked whether they wanted service contracts on those PDPs (11/23 or 11/03 IIRC), the answer was "Nah, they're just consumables".

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  6. Duncan Macdonald

    RSX11M - Dave Cutler

    Anyone who read the RSX11M sources (driver writers especially) realised that Dave Cutler was a very very good programmer long before he worked on VMS and later Windows NT. He managed to get a multiuser protected general purpose operating system to work with a minimum memory footprint of under 32kbytes on machines with about the same CPU power as the chip on a credit card. (A 96kByte PDP 11/40 (1/3 mip) with 2 RK05 disks (2.4Mbyte each) could support 2 concurrent programmers - a PDP 11/70 (1 mip) with 1Mbyte and 2 RM03 disk packs (65Mbyte each) could support 10 or more.) During the many years that the CEGB used PDP-11 computers with RSX11M, I did not hear of a single OS failure that was not caused by a hardware fault - I wish that current systems were as good.

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    1. Anonymous Coward
      Reply Icon
      Anonymous Coward

      Re: RSX11M - Dave Cutler

      A few years ago I had RSX11 running in SIMH, so I'm wondering if that's an option for these kinds of embedded and SCADA systems. After all, it's not the software that's likely to fail - it's the ancient hardware, and although there is at least one company out there producing PDP-11 clones it's surely easier to use a simulator that can be modified if an overlooked hardware quirk crops up.

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    2. MD Rackham
      Reply Icon

      Re: RSX11M - Dave Cutler

      Of course, that was several years after there was a protected, multi-user timesharing system running on the PDP-8, TSS/8. And it would run in 8K of memory, although you had to spring for 12K for decent performance. Swapped off a fixed-head 256K word disk.

      You PDP-11 kids get off my lawn!

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  7. Denarius
    Meh

    there are alternatives

    Why not migrate to QNX ? If remaining on old kit and OS, the biggest issue is hardware replacement. I assume they must have piles of old kit in back of warehouse.. Even then, capacitors age and leak, resistors drift, transformers let smoke out etc. Hardware unreliability will take the best of OS and apps.

    I do acknowledge these old machines were built to last. Still remember the only VAX I had to support. Only an anti-tank shell could have hurt it.

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    1. Peter Gathercole Silver badge
      Reply Icon

      Re: there are alternatives

      It depends on the model, but many of the UNIBUS PDP-11s were built out of TTL (even the CPU and FPU). This means that it should still be able to source and fit almost any of the silicon parts, although I suspect that the most difficult parts to source would be the memory chips.

      If they were F11 or J11 systems, you would have to rely on existing parts.

      But I suspect that with the state of current chip baking technology and the simplicity of the chips back then, it may be possible to create a pin compatible memory chip using an FPGA relatively easily if it were really necessary.

      Hmmm. What a project. Keep PDP-11 alive using FPGAs!

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      1. Bob H
        Reply Icon
        Go

        Re: there are alternatives

        @Peter Gathercole

        There is already a well established PDP-11 project on OpenCores:

        http://opencores.org/project,w11

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        1. MacroRodent
          Reply Icon

          Re: there are alternatives

          The Soviet Union used to produce PDP-11 clones: the SM-4. I actually first encountered Unix on one of those. It was running at the Helsinki University of Technology in the 1980's. The Unix version was odd, my instructor described it as being halfway between 6. and 7. edition Unix. (I'm not sure if it also came via the SU, or was hacked together at the University).

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      2. frank ly
        Reply Icon

        Re: there are alternatives

        Wouldn't it be easier to make a hard/software PDP-11 emulator that was power plug and I/O plug compatible with the PDP-11? It would be a lot smaller for a start.

        (In the late '70s, as a student engineer, it was my task to boot up a Nova-820 (?) every morning by setting toggle switches and similar retro activities. Ahhhh, those were the days.)

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        1. annodomini2
          Reply Icon
          FAIL

          Re: there are alternatives

          They would never redesign the system, if the system has issues, they are known and fixes are well known.

          Changing the system design introduces potential risks and unknowns into the system.

          It's not about Zero failure, it's about safe and predictable failure.

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        2. Steve I
          Reply Icon
          Go

          Re: there are alternatives

          "Wouldn't it be easier to make a hard/software PDP-11 emulator that was power plug and I/O plug compatible with the PDP-11? It would be a lot smaller for a start."

          Brilliant idea. There must be a good use for the space saved, and if it wasn't 100% compatible, why - what's the worst that could happen?

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    2. Anonymous Coward
      Reply Icon
      Anonymous Coward

      Re: there are alternatives

      "Why not migrate to QNX ?"

      Because then the application would have to be rewritten and recertified?

      Hardware is probably not the big problem in this picture, PDP11 hardware was generally of sufficient quality and sufficiently well documented that replicating old PDP11 in new silicon (or even via software emulation e.g. via SIMH) would not be a big challenge in general. But in the nuclear industry, special care might be needed (SIMH might not be acceptable, for instance).

      Depending on the application, there might even be a master/standby setup to protect against routine hardware failures.

      But re-doing the application from scratch, just so it can run under QNX?

      Where's the benefit (in these particular circumstances)? There would certainly be lots of cost.

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    3. Bastage
      Reply Icon
      Go

      Re: there are alternatives

      There is replacement hardware available. NuPDP replacment CPU's including QBUS support and peripheral cards. Also NuVAX for the new kids.

      The Reviver boards for PDP-11 and HP1000.

      The Osprey PDP-11 and Kestral HP1000 hardware from Strobe Data.

      There are also the Stromasys/Charon software emulators VAX/AXP/HP3000.

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    4. Alan Brown Silver badge
      Reply Icon

      Re: there are alternatives

      WRT "resistors drift" - that hasn't been an issue since carbon stopped being used - unless you smoke 'em of course.

      My experience of transformers smoking is "only if left switched off for long periods - it's usually water which does 'em in and one in use is invariably warm enough to stay dry.

      There's a hell of a lot to be said for keeping spares in sealed baggies, or even better in sealed baggies with an inert atmosphere.

      In the old days ESR on electrolytics was so high that you'd always slug 'em with a small ceramic nearby. Cost saving/"better design" means that's no longer done, plus they're run a lot closer to their voltage rating (Generally one would use 25V parts on a nominal 12V line to ensure switching spikes didn't take 'em out.) and I believe _that_ is a major contributor to modern failure rates.

      Vintage electronics is a field all to itself. There are as many (or more) failures from poorly made joints or crudded up connector pins as there are down to actual genuine faulty components (although I have seen a 1972-vintage audio IC which succumbed to the Purple Plague - once in my entire career of servicing thousands of the bloody things.)

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      1. Jim 59
        Reply Icon

        Re: there are alternatives

        purple plague ?

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  8. Admiral Grace Hopper
    Thumb Up

    ICL VME

    is still in revenue service and will be for the foreseeable future. It may be an emulation tucked away in the corner of a SLES box these days, but it's still there, ticking away like it's the early 80's.

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    1. Steve I
      Reply Icon
      Go

      Re: ICL VME

      "emulation tucked away in the corner of a SLES box".

      Probably even a SNES would be enough.

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    2. Stevie
      Reply Icon

      Re: ICL VME

      "is still in revenue service"

      Well, it was bound to catch on eventually. Did they ever stop it throwing away all the diagnostic info when the stack overflowed? Cheapest panic dump printouts ever.

      When ICL were trying to sell it it was notable that almost everyone using a 2900 was running DME, which looked like George.

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  9. Bob Dunlop

    Hey I was taught assembler programming using a pdp11 .

    After it's nice clean structure, the mess that was 8086 code came as quite a shock.

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    1. This post has been deleted by its author

    2. Frederic Bloggs
      Reply Icon

      George 3 for me!

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      1. Martin Gregorie
        Reply Icon

        "George 3 for me!"

        - preferably running applications written in PLAN3 or Algol68R

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      2. Philip Lewis
        Reply Icon
        Boffin

        George 3

        George 3 was my introduction to computing. There was also RSTS/E on the 11/70 which I fancied much more (surprise, not). In any case, it was all onward and upward after that.

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        1. Tristram Shandy
          Reply Icon

          Re: George 3

          George 3 was excellent......Automatic off-loading when the Filestore was getting crowded, perfect for job control which was much more powerful than IBM's JCL. When ICL replaced the 24-bit 1900 range with the 32-bit 2900 range running VME/B many outfits continued to use George 3 under DME emulation to keep their old programs running.

          VME/B was so resource hungry that 1900 programs actually ran much faster than native 2900 ones. Rumour had it that ICL had built in delay loops in the DME emulation to slow it down so as to encourage the move to the native VME/B environment. (But it possibly was just a rumour).

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