First 3-D processor runs at 1.4 Ghz on new ar...(rom any point on any level to its destin...)

Complicate that by changing the two United States layers to something like China and India where the driving laws and roads are quite different, and the complexity and challenge of designing a single control system to work in any chip begins to become apparent, says Friedman.

Since each layer could be a different processor with a different function, such as converting MP3 files to audio or detecting light for a digital camera, Friedman says that the 3-D chip is essentially an entire circuit board folded up into a tiny package. He says the chips inside something like an iPod could be compacted to a tenth their current size with ten times the speed.

What makes it all possible is the architecture Friedman and his students designed, which uses many of the tricks of regular processors, but also accounts for different impedances that might occur from chip to chip, different operating speeds, and different power requirements. The fabrication of the chip is unique as well. Manufactured at MIT, the chip must have millions of holes drilled into the insulation that separates the layers in order to allow for the myriad vertical connections between transistors in different layers.

"Are we going to hit a point where we can't scale integrated circuits any smaller? Horizontally, yes," says Friedman. "But we're going to start scaling vertically, and that will never end. At least not in my lifetime. Talk to my grandchildren about that."

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