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"OH WATERS, TEEM WITH MEDICINE TO KEEP MY BODY SAFE FROM HARM, SO THAT I MAY LONG SEE THE SUN." - Rig Veda
The human brain runs on only about 20 watts of power, equal to the dim light behind the pickle jar in your refrigerator. By contrast, the computer on your desk consumes a million times as much energy per calculation. If you wanted to build a robot with a processor as smart as the human brain, it would require 10 to 20 megawatts of electricity. “Ten megawatts is a small hydroelectric plant,” Boahen says dismissively. “We should work on miniaturizing hydroelectric plants so we can put them on the backs of robots.” You would encounter similar problems if you tried to build a medical implant to replace just 1 percent of the neurons in the brain, for use in stroke patients. That implant would consume as much electricity as 200 households and dissipate as much heat as the engine in a Porsche Boxster.
“Energy efficiency isn’t just a matter of elegance. It fundamentally limits what we can do with computers,” Boahen says. Despite the amazing progress in electronics technology—today’s transistors are 1/100,000 the size that they were a half century ago, and computer chips are 10 million times faster—we still have not made meaningful progress on the energy front. And if we do not, we can forget about truly intelligent humanlike machines and all the other dreams of radically more powerful computers.
Getting there, Boahen realized years ago, will require rethinking the fundamental balance between energy, information, and noise. We encounter the trade-offs this involves every time we strain to hear someone speaking through a crackly cell phone connection. We react instinctively by barking more loudly into the phone, trying to overwhelm the static by projecting a stronger signal. Digital computers operate with almost zero noise, but operating at this level of precision consumes a huge amount of power—and therein lies the downfall of modern computing.
In the palm of his hand, Boahen flashes a tiny, iridescent square, a token of his progress in solving that problem. This silicon wafer provides the basis for a new neural supercomputer, called Neurogrid, that he has nearly finished building. The wafer is etched with millions of transistors like the ones in your PC. But beneath that veneer of familiarity hides a radical rethinking of the way engineers do business.