Sun Labs' Proximity Communication Closely Quartered Chips

Data makes the leap between chips, creating communication that's 60 times faster.

Medical researchers imagine a day when gene-mapping simulations will take an hour or two to compute instead of a week, on systems that process data up to 100 times faster than they do today. That dream could become a reality in the next five years with technology called proximity communication that's under development at Sun Microsystems Laboratories in Menlo Park, Calif.

For years, Sun has been looking for ways to "get computers back on the improvement curve they've fallen off of," says principal research scientist Robert Drost. While processor speeds have improved up to 4,000%, I/O speeds have improved by a factor of just 10 to 15. Proximity communication could catapult I/O speeds into the stratosphere.

In early 2000, research fellow and Sun Labs Vice President Ivan Sutherland hatched an idea while visiting his friend Steve Jacobson at Sarcos Research Corp., a Salt Lake City-based manufacturer of robotics and advanced prosthetics. Developers there were using a process called capacitive sensing to measure minute shifts in the movement between a chip and a glass plate -- movements as small as one millionth of a centimeter.

Sutherland hypothesized that if tiny mechanical movements could be accomplished through capacitive sensing, then surely it should be possible to put chips next to one another and send data using that same physical phenomenon.

Sutherland developed chip-to-chip communication technology and then enlisted the expertise of Drost, who at 34 was named to the 2004 list of the world's 100 Top Young Innovators Under Age 35 by MIT's Technology Review.

Proximity communication is a process where two chips, each with transmitter and receiver circuits, are positioned extremely close to each other. Without wires or soldered connections, data is transmitted across the gap by "capacitive coupling," which is coupling between charged particles that are at rest. Fewer wires and connections mean fewer bottlenecks in multiprocessor computers.

Very fast communications could reduce the need for big on-chip caches, freeing up real estate for other processing functions, Drost says.

The result: The technology could enable processor chips to communicate 60 times faster and with 30 times less energy than is possible using conventional circuit boards.

Proximity communication relies on chips that are placed very close together -- a tough configuration to manufacture in high volumes at a low cost.

To compensate for misalignment between chips, Sun researcher Robert Bosnyak and Chief Technology Officer Greg Papadopoulos developed a technique called electronic alignment that allows the transmitters and receivers on each chip to shift positions to compensate for a few hundred microns of misalignment.

"That was absolutely critical," says Drost. "Before that, [proximity communication] seemed really interesting but impractical."

Drost says he expects proximity communication to greatly improve the speed of applications requiring high-performance computing, such as weather modeling, car-crash simulations or drug simulations.

In 2003, the U.S. government awarded Sun Labs a $50 million Defense Advanced Research Projects Agency contract to help design next-generation supercomputers. That project will be completed in 2010, but proximity communication technology will show up in other applications before then, Drost says. When that happens, he adds, "it's a whole different ballgame."

Collett is a Computerworld contributing writer. Contact her at

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