...With the supply of capital, we wouldn't have had enough money to build them at a high enough rate, and we would have struggled with logistics, with just moving the boxes."
To meet the demand Raspberry Pi struck a deal with major electronics distributors Premier Farnell and RS Components and licensed them to manufacture and distribute the boards. Partnering with the electronics distributors gave the operation the buying power to keep component prices low and the global distribution network to handle the logistics.
Boards were originally made in China but from September last year some of the manufacturing was moved to the Wales. The Sony factory in Pencoed in South Wales now produces 4,000 boards each day.
The Raspberry Pi is sold at just above cost price, and even though the Foundation is sharing that profit with the two distributors, Upton said it still has enough money to pursue its charitable aims.
"We're not rolling in cash but we do have enough money," he said. Those aims range from lobbying government about IT curriculum reform to attending conferences, preparing teaching materials and setting up programming competitions.
The reasoning behind the Raspberry Pi wasn't to head off some future IT skills crisis — Upton says the crisis is already here.
In his day job Upton is a system-on-a-chip architect at chip designer Broadcom and says he sees firsthand the evidence of the lack of new computer scientists, software engineers and programmers coming out of UK universities.
"It's an industry with a lot of niches and when I look around at Broadcom there aren't enough guys in their 20s. There should be the same ratio of guys in 30s to guys in their 20s, but there are a lot more guys in their 30s. It's not a dying industry yet but if we carry on, we'll probably fall below a critical mass and we won't be sustainable anymore," he said.
The question of whether there is a shortage of computer programmers and engineers in the UK is a contentious one, with figures suggesting its effects are sometimes overstated. The number of advertised IT roles in 2011 stood at little over half those advertised in early 2008. Some IT skills crisis sceptics say the domestic talent shortage is overblown to justify the offshoring of entry-level roles.
Upton's take is that he sees little evidence that there is software engineering talent going begging in the UK.
"If I was besieged at Broadcom with talented applicants, then I would believe that, but I'm inclined to believe this is bullshit," he said.
Sales of the Raspberry Pi board are split about one third in the UK, one third in North America and one third in the rest of the world. Outside the UK and US most sales are in Europe. They remain relatively weak in China, India and South America.
"I think that Britain had the strongest 1980s indigenous computer culture and that a lot of the early Pi adopters are people like me who had a BBC Micro" — Eben Upton
"We're strongest in the UK, I think for two reasons," Upton explained. "One, we've had an enormous amount of support from the press and people in general. I also think that Britain had the strongest 1980s indigenous computer culture and that a lot of the early adopters are people like me who had a BBC Micro."
Early adopters of the Pi were in general not children with an interest in programming, but men with passion for computing who saw a cool new toy for them to hack. Grown-up tech enthusiasts accounted for about four-fifths of sales at launch according to Upton but the pendulum is now swinging back towards kids, as both parents, teachers and children buy the boards. He estimates that hundreds of UK schools have also picked up the device for use in lessons.
The enthusiast community has been busy building the Pi into creations of every shape and size, from self-piloting ships to remote-controlled homes. One of Upton's favourite mods was a project that attached the Pi to a balloon and sent it to "near-space", about 30km up where there is just one percent atmosphere and temperatures drop to -50°C.
"I'm a real space cadet. I love those pictures that he gets from 40km up with the blackness of space," he said.
Businesses are also increasingly finding a use for the diminutive board, and since it became possible to bulk-order the Pi, Premier Farnell has seen an upsurge in large volume orders — those running into hundreds of boards.
Upton said that businesses are buying up the board to use for tasks ranging from automating factory production lines to running consumer media player appliances.
"Industrial computers typically cost a few hundred dollars and they're typically much less good than the Pi," Upton said, adding the Pi provided a low-cost computing alternative for these niche applications.
"There are lots of little industrial verticals. None of them on their own are big enough to justify somebody coming in and making something that can address that market. What the Pi has done is to make a multi-tool."
Upton believes that demand for the Pi will sit close to its current level, of between 100,000 and 200,000 units a month, for another year.
"There's always the concern that it might tail off. [But] I think there's enough demographics and enough geographies that we haven't hit yet that we can keep going for a bit," he said.
The Raspberry Pi Foundation doesn't share...