How cheaply can you build a supercomputer?  A group from the University of Southampton just made one using 64 Raspberry Pi ARM GNU/Linux boxes ($25 each) and Lego blocks. The machine, named "Iridis-Pi" after the University's Iridis supercomputer, runs off a single 13 Amp mains socket and uses MPI (Message Passing Interface) to communicate between nodes using Ethernet.

The team was led by Professor Simon Cox and included Richard Boardman, Andy Everett, Steven Johnston, Gereon Kaiping, Neil O'Brien, Mark Scott and Oz Parchment.  Professor Cox's son, six-year-old James Cox, assisted with specialist support on Lego and system testing.

The racking was built using Lego with a design developed by Cox and son.  The whole system cost under £2,500 (excluding switches) and has a total of 64 processors and 1Tb of memory (16Gb SD cards for each Raspberry Pi). Cox uses the plug-in 'Python Tools for Visual Studio' to develop code for the Raspberry Pi.

Professor Simon Cox and technology specialist James with Iridis-Pi. Credit: University of Southampton.

"As soon as we were able to source sufficient Raspberry Pi computers we wanted to see if it was possible to link them together into a supercomputer. We installed and built all of the necessary software on the Pi starting from a standard Debian Wheezy system image and we have published a guide so you can build your own supercomputer," said the elder Cox. "The first test we ran - well obviously we calculated Pi on the Raspberry Pi using MPI, which is a well-known first test for any new supercomputer. The team wants to see this low-cost system as a starting point to inspire and enable students to apply high-performance computing and data handling to tackle complex engineering and scientific challenges as part of our on-going outreach activities."

Young James added, "The Raspberry Pi is great fun and it is amazing that I can hold it in my hand and write computer programs or play games on it."

He's not kidding. The six-year-old used Python and Scratch over the summer to program the Raspberry Pi himself. 

Have some Legos and $1,600 laying around (hey, the UK charges more for everything but they get free check-ups)? They put the instructions up here and now you can build your own supercomputer. Take that, Instructables.