The European Union has decided to back a research programme managed by IBM's research lab at Zurich to look at whether tiny relays may make more sense than regular CMOS transistors in the future. In one sense, it's a back-to-the-future move that harks back to a long-lost computer - bombed to smithereens by the Allies in the middle of the Second World War.

Trying to develop a computer that would help design aircraft, Konrad Zuse opted for electromechanical relays because he considered them - quite rightly as it turned out - to be more reliable than thermionic valves. However, it was buried under tonnes of rubble in 1941 just two years after completion and the idea of relay-based logic was buried with it. The post-war designers of the somewhat flakier valve machines set the scene for what computer architecture to what it is today. The only relays in the computer room are the ones controlling the power.

Fast forward to this century and we find the transistor-based architectures, which evolved from their valve-filled forebears, are running out of steam. Thermodynamics issues place a lower limit on the power consumption of a silicon transistor. For years, we have been winding down the voltage used to supply power to transistors and this has paid off in lower energy usage. But there is a limit to how far you can go before leakage through a transistor that should be turned off becomes the main consumer of power. We are now very close to that limit.

The good thing about a relay is that, because there is no electrical contact between two sides of circuit when it's switched off, there is no leakage. And we have a technology that can make miniature relays: the microelectromechanical systems (MEMS) technology used to build the accelerometers used in iPhones and Wii motes. Put those two together and it looks as though you have a plan for the future computing. Almost.

For one thing, the MEMS switches are mechanical: reliability could be a problem. However, researchers at the University of California at Berkeley, who have done a lot of work on nanorelays already, have found that MEMS switches are reliable enough for at least a quadrillion on-off cycles. That actually is not quite as many as you'd like for a regular computer but the nanorelay's other problem means it is not a showstopper.

Speed is the other problem. The relays cannot open and close circuits as quickly as a regular transistor. In fact, they can be much slower so don't expect to buy a personal computer running relay logic any time soon. Speed and a quadrillion operations points to a different market: for small, battery-powered sensors and actuators. The kinds of chips that go into smart meters and structural-health monitors for bridges or aircraft. A quadrillion operations supports a 100MHz processor that only runs one second out of each hundred over a ten-year lifespan.

As a result, relay-based logic is not the future for electronics. But it has a future.

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