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Friday, March 23, 2007

Computer data through a laser beam

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A start-up company has developed an unusual way to use lasers to speed the flow of data inside a computer, hoping to break a bottleneck that can hamper machines using many microprocessors.

The company, Lightfleet Inc., plans to sell servers it predicts will be much more efficient than existing systems in tackling tough computing problems. The tasks could include automatically recognizing a face in a video image or sifting through billions of financial transactions for signs of illegal activity.

Researchers for years have been trying to handle such chores with variants of parallel computing -- gang-tackling problems with chips or systems that use the equivalent of many electronic brains. Getting answers to complex calculations can be slowed as each microprocessor waits for data being processed by other chips.

Networks inside most servers can easily pass a message from a single microprocessor to another. Congestion can arise as many chips try to simultaneously send messages to many others. Lightfleet said new servers it plans to begin selling next summer, which will use 32 dual-processor chips from Intel Corp., can do such feats easily.

Engineers at the closely held Camas, Wash., company decided to exploit lasers -- but not in the way they are usually used for communications. Ordinarily, such optical-networking devices send tightly focused pulses of light down stands of fiber-optic cabling.

Lightfleet is doing the opposite: using lenses to spread out laser beams and bounce the light off a mirror to send data around a system. Each microprocessor is installed with a laser transmitter and a set of devices that receive beams of light carrying messages from other chips. The light is reflected off the mirror and passes through focusing lenses to the receivers.

Messages from each processor, or any combination of them, are simultaneously sent to all the other microprocessors. Each receiver only picks out the messages intended for it, because of special addressing information sent with the light beams.

The design is particularly efficient at sending "all-to-all" messages between chips in a system, said Bill Dress, a Lightfleet senior scientist and co-inventor of the technology. Because the system sends light through air, Lightfleet avoids the need for wiring and associated switching circuitry and software, he adds.

Convincing the market about an unfamiliar technology is a tall order, Mr. Hewitt said; fully exploiting Lightfleet's technology could require rewriting programs. One skeptic is Steve Scott, chief technology officer at supercomputer maker Cray Inc. He said conventional electronic connections inside such machines already distribute data adequately; the real bottleneck, he said, comes from the connecting pins on chips that limit how fast they can send and receive data. Mr. Scott questions whether laser-based connections are worth the added cost.

Some scientists are eager to try it, including those at Oregon State University's College of Oceanic and Atmospheric Sciences. Big computers there combine data from an array of sensors to model complex phenomena, such as the way climate changes affect ocean currents and micro-organisms.

Those complex calculations are limited by how quickly processors can communicate, said Charles Sears, manager of research computing for the college. After being briefed on Lightfleet's technology, "we said this looks pretty exciting," added Mark Abbott, dean of the college.

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