The next major advance in computer processors will likely be the move from today's two-dimensional chips to three-dimensional circuits, and the first three-dimensional synchronization circuitry is now running at 1.4 gigahertz at the University of Rochester.
Unlike past attempts at 3-D chips, the Rochester chip is not simply a number of regular processors stacked on top of one another. It was designed and built specifically to optimize all key processing functions vertically, through multiple layers of processors, the same way ordinary chips optimize functions horizontally. The design means tasks such as synchronicity, power distribution, and long-distance signaling are all fully functioning in three dimensions for the first time.
But with vertical expansion will come a host of difficulties, and Friedman says the key is to design a 3-D chip where all the layers interact like a single system. Friedman says getting all three levels of the 3-D chip to act in harmony is like trying to devise a traffic control system for the entire United States—and then layering two more United States above the first and somehow getting every bit of traffic from any point on any level to its destination on any other level—while simultaneously coordinating the traffic of millions of other drivers.
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.
Eby Friedman has written a book on three integrated circuit design.
V. F. Pavlidis and E. G. Friedman, Three-Dimensional Integrated Circuit Design, Morgan Kaufmann, 2008, ISBN # 978-0-12-374343-