back to article New guide: Bake your own Raspberry Pi Lego-crust cluster

Scientists at the University of Southampton have built a "supercomputer" from Raspberry Pis lashed together to form a colourful data-cruncher. Professor Simon Cox and his team racked up 64 credit card-sized Pis using Lego building blocks to create the parallel computer. They named their beast Iridis-Pi after the university's …

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    1. Nigel 11

      Re: Great.. .but better ways to do the power...

      A PC power supply will be VERY unhappy supplying many amps at 5V and none at 12V. It may refuse to work with that load, overheat and emit smoke, or simply waste a large fraction of the power going in. They're designed for use with modern PC hardware, with the lion's share of the power being consumed at 12V.

      Just source a single-voltage power supply that delivers enough amps at 5V. There will be plenty of PSUs to choose from at RS or CPC. It may be cheaper to use multiple 5V 4A or 5A "bricks" than a single (say) 40A unit, and may also be easier to wire up.

      1. Anonymous Coward
        Anonymous Coward

        Re: Great.. .but better ways to do the power...

        "A PC power supply will be VERY unhappy supplying many amps at 5V and none at 12V."

        Could you string a bunch of 7805s (http://www.raspberrypi.org/phpBB3/viewtopic.php?f=62&t=14512) off the 12V rail?

        Or now that you can back-power (if I read it correctly) off a USB hub with the new revision... maybe(?)

        1. Stoneshop
          FAIL

          Re: Great.. .but better ways to do the power...

          Err, you don't use 7805's if you need to drop 7V at 700mA, you use a step-down converter. But a simple 5V PSU with sufficient capacity will cost about the same as the hardware you need to power half the cluster off a 12V rail.

        2. Pet Peeve
          Boffin

          Re: Great.. .but better ways to do the power...

          You could do that, the 7805 is a really nice chip. You'd need to wire up a bunch of them and screw them to a heatsink though. It's less work to use a powered USB hub, which would at least let a bunch of pies share the same wallwart.

          What a mess of power cables! With my supernatural ability to get myself tangled in cords, I would have had this thing in pieces on the floor in minutes. Seriously, in the days of corded phones I frequently tied myself to my own chair if I got engaged in conversation for a while.

      2. Paddy 1

        Re: Great.. .but better ways to do the power...

        You can get 50A 5V supplies from hong kong for under £30

      3. Stoneshop

        Re: Great.. .but better ways to do the power...

        A PC power supply will be VERY unhappy supplying many amps at 5V and none at 12V

        So far, none of the several dozen PSU's I've mistreated that way have refused to work. The only thing that will actually happen is that the voltage on the unloaded buses will rise a bit (the 5V output is the one used for regulation feedback) and this *may* cause some overvoltage limiter to kick in and shut the thing down, but this is not something I have encountered even once. It may be true of PSUs meant to power gaming systems with graphics cards that contribute significantly to global warming, run-of-the-mill PSUs can be used without mishap.

    2. Naughtyhorse

      Re: Great.. .but better ways to do the power...

      I do wish people wouldnt say "amperage" its so clumsy

      "sufficient current" will suffice! in both senses.

      </pedantage>

  1. chris 50
    Pint

    Building better worlds

    I would have said they are taking liberties using the term "supercomputer" until I noticed the Lego.

  2. tommitytom
    Thumb Up

    I love...

    ...everything about this!

  3. ukgnome
    Pint

    Awesome

    Been into clusters for a while, but this one makes me all fuzzy.

  4. Michael H.F. Wilkinson Silver badge
    Thumb Up

    Lovely idea!

    I think I will show this to my students when next I lecture on parallel computing

    1. James Hughes 1

      Re: Lovely idea!

      And that's the real point - although a cluster (Bramble) of raspi's doesn't have a very good performance figure on cycles per $, compared with a desktop for example, its is VERY cheap as a teaching device for parallel processing.

      If course, if you could access to the GPU, you have 48 processors per Raspi to play with.

  5. Mark Honman

    Got Occam?

    Hmm, if every family member gave me a Pi for Xmas that would be a decent start.

    from the enquiring minds want to know (and are presently too lazy to read the blog) dept:

    * can the graphics part of the Pi processor be used as a floating-point vector processor?

    * what is the computation/communication performance ratio?

    * Linpack performance?

    I guess it will all become clear in time...!

  6. Some Beggar

    The IDEs of March.

    Is the Visual Studio plugin the only python IDE that supports debugging parallel doohickeys using MPI?

    Because I'd quite like to knock up something like this but I am terminally allergic to Visual Studio.

    1. Charlie Clark Silver badge

      Re: The IDEs of March.

      I think I-Python (from the SciPy project) has support for MPI and I'm sure other environments do.

      1. Some Beggar

        Re: The IDEs of March.

        Ta!

  7. proto-robbie
    Pirate

    Reconstruction in Lego, please...

    arf arf

    1. Anonymous Coward
      Anonymous Coward

      Re: Reconstruction in Lego, please...

      Lol

    2. Anonymous Coward
      Anonymous Coward

      Re: Reconstruction in Lego, please...

      Don't be daft. It'll be playmobil around here...

  8. Anonymous Coward
    Anonymous Coward

    Danger?

    "It's not in danger of threatening IBM's Sequoia beast..."

    As if Sequoia will hunt you down if you do over take it.

  9. Mad Hobbit

    Graphics

    I wonder how good these would be for ray-tracing/CGI? Have seen other articles on using a bunch of MBs to make a "supercomputer" that is the backbone for home CGI work.the articles claimed about a 15X speed up due to sending out the frames to all the cpus at once.

    Maybe the Professor could get with the graphic arts dept and run a few benchmarks

    It is really a good project. well done.

    1. Frumious Bandersnatch

      Re: Graphics

      Probably not very good. Ray tracing tends to exercise the I/O an awful lot so even if you assign one pi to a particular section of the screen it'll still end up accessing other parts of the scene in a pretty random access pattern (rays bounce). With only a 100MBit connection (and the fact that the USB and Ethernet share a bus) it's easy to saturate the available data channels--a problem that only gets worse as you scale up (though working with different net topology and having more control nodes could definitely help, to a degree).

      On the other hand, having the farm render a typical fractal image would be a perfect application for it since each screen section is typically independent of each other one.

      Despite how impractical this thing is, I'd still love to have one. I'm sure it's also a great teaching resource in spite of (nay, even because of) its shortcomings, necessity being the mother of invention and all that.

  10. Martin Maloney
    Coat

    Why do I always have to be the one?

    Q: What do you say to someone who is trying to steal your Raspberry Pi cluster?

    A: Lego!

  11. Kubla Cant
    Go

    If you don't know what to do...

    ... here's what looks like an interesting course on the Cambridge Computing Labs site.

    I intend to work through it as soon as I have (a) a Raspberry Pi and (b) a lot more free time.

  12. James 36
    Thumb Up

    title

    love this, seems like a cost effective way to get to get people into programming for HPC,

    which cannot be a bad thing

  13. Andus McCoatover
    Windows

    As usual, I'm missing something on the PSU front...

    ..Or am I? It's a piece of piss to downconvert 220 volts down to 5V with a switch-mode PSU. Jesus H. Wept, I did it a quarter of a century ago, when I was in my ealy 20's. About 90% efficiency, and I used an optical coupler for the feedback, and a 555 timer to fire the input transistors....(Fed by a humongous resistor, an effing big zener diode, and a bag of capacitors I could barely afford (low ESR)

    Bloody wound the (toroidal) transformer myself. IIRC, I used a strip of copper, covered with sellotape for insulation, wrapped around the toroid, about 10 turns, to get the secondary output working....

    OK, a few explosions on the prototypes, but.... My University Professor would have wet himself laughing, except...I never went to University...Self-taught from having no girlfriend worth mentioning, so living in my mom's house.....Nothing else to do....

  14. Anthony Gamble

    Technical Manager

    The world's first Raspberry bush!

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