The next step towards the computers of the future has been taken, after engineers from Stanford University built the first working computer that uses carbon nanotube transistors (CNTs).
The machine is rudimentary, but it is running a basic operating system, and can perform calculations, but it probably wouldn’t stand up to the rigours of GTA 5. It’s most important as proof of concept, that computers can be made of more efficient materials
Currently, computer processors are made out of silicon, an element that has so far done everything asked of it. However, as the art of miniaturisation improves, computer scientists are beginning to realise it has a limit to its abilities.
According to Moore’s Law, formulated in 1965, the density of transistors – and, effectively the processing power of computers – doubles every two years. But as silicon processors have become smaller and cheaper, so too have they become hotter.
"Energy dissipation of silicon-based systems has been a major concern," said Anantha Chandrakasan, head of electrical engineering and computer science at MIT. He described the Stanford team’s work as "a major benchmark" in moving CNTs toward practical use.
CNTs are long chains of carbon atoms that are especially efficient at conducting electricity. They are extremely thin – thousands of CNTs could fit side by side in a human hair – meaning that it takes very little energy to switch them off, and making them more suitable, in theory, to handle the heat that silicon has trouble dissipating.
There are still kinks to iron out; although CNTs have obvious advantages, they do not always grow in the neat lines that chips require, and the assembly process can sometimes produce metallic imperfections, which will cause transistors to short circuit.
These flaws have presented serious barriers to CNTs in computer manufacture in the past, so the team had to develop an new way to construct them.
"We needed a way to design circuits without having to look for imperfections or even know where they were," he said.
To eliminate the metallic nanotubes, the team developed an "imperfection-immune design", in which all the regular CNTs were switched off, before flooding the semiconductor circuit with electricity, thereby burning out the faulty, conductive nanotubes, and leaving only the usable ones.
In order to deal with the CNTs’ natural misalignment, meanwhile, researchers designed an algorithm to maps out a circuit layout that would be guaranteed to work no matter whether or where CNTs might be askew.
So while the Stanford computer might only have 178 transistors – as opposed to the 5bn that the Xbox One is threatening to house – the fact that it works is significant.
"People have been talking about a new era of carbon nanotube electronics moving beyond silicon," said Subhasish Mitra, one of the professors who lead the research. "But there have been few demonstrations of complete digital systems using this exciting technology. Here is the proof."
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