Intel researchers are shedding some light on a potential new application for chip photonics: upping the performance of multicore processors.
The processor giants research labs are exploring ways to use silicon photonics—on-chip components that use light to transmit data—to replace electrical interconnects using copper wiring and simultaneously speed up vital connections that move data into and out of processors.
Intel thinks that electrical interconnects will continue to be used for some time to come, but that optical eventually will win out as it becomes more difficult to wring performance out of copper wires.
Creating bus that can move more data is vital to Intel as the chip maker moves deeper into the realm of multicore chips. Intel recently introduced dual-core Pentium desktop processors, which have two individual processor cores inside a single slice of silicon, where previous chips had only one.
It will begin rolling out dual-core notebook and server chips later this year. It follows that future generations of its processors will grow to have four, eight or more cores. Intel must come up with a data pipeline to meet those needs.
“The potential here is for silicon photonics to be used as the technology to underpin future optical busses” for multicore PC processors, said Manny Vara, a technology strategist at Intel Corp.s research and development labs.
When it comes to designing computers with a chip that sports a large number of cores, “the problem is feeding [the chip] … so its not sitting there doing nothing,” Vara said. Not to mention, “once its done with the data, how do you get it out? How do you connect it with other components, because those are getting faster as well?”
Silicon photonics could be an ideal because of its potential to offer very high bandwidth—Intels already got gear running at 10 gigabits per second in its labs—and its ability to be designed directly into the chip itself, Vara said.
Others, including Startup Luxtera Inc., are also working on silicon photonics gear. Luxtera, which is working on a light modulator that works to convert light signals into data, hopes to build it into silicon next year. The company has been working with Freescale Semiconductor Inc.
But Intel believes it can do it all—manufacturing all of the necessary components, including lasers, in-house using its standard chip-manufacturing techniques. That result, aside from helping to lower costs, is the ability to add the connections directly to its own chips, thus creating desktop, notebook and server processors with optical busses built-in, Vara said.
Its working now to create prototype silicon photonics interconnects that can link racks of servers. Intel believes these rack-to-rack interconnects could appear first, within about three to five years.
Circuit board-to-circuit board connections would arrive next. Chip-to-chip connection would arrive last, likely in five years or more, somewhere in the 2010 or later time frame, according to documents published by Intel.
Next Page: Getting silicon photonics ready for prime time.
Prime Time
Intel still has some work to do before silicon photonics are ready for prime time, company researchers say. For one, it has yet to create prototype chips that use silicon photonics-based busses, Vara said.
Instead, the labs are working on each individual component required for silicon photonics as well as boosting the overall bandwidth they can achieve and ensuring their manufacturability in silicon, said Marco Paniccia, director of Intels Photonics Technology Lab.
“Theres a lot of fundamental issues and research we need to do here,” Paniccia said.
But earlier this year, Intel announced that it had succeeded in building a laser in silicon. The laser is vital as it can serve as the light source for silicon photonics interconnects.
Such breakthroughs serve not only as scientific proof points, but they help to remove physiological barriers, Paniccia said.
But Intel researchers are still working on how to create and integrate the various elements of a silicon photonics system, including lasers, photo detectors that read and convert the data, and waveguides for carrying light inside chips.
“Everything we do has to be under the presumption that its CMOS-compatible” and that it can be “fabricated using todays technology alongside existing products,” Paniccia said.
But so far, Intel has discovered that silicon photonics doesnt need leading-edge, 90-nanometer manufacturing. Its developed its technology inside older chip plants.
Still, integrating silicon photonics with chips just for the sake of integration is “useless,” Paniccia said. “It has to be smaller, better, faster. Otherwise, stay with discrete, because the penalty you pay is in [manufacturing] yields.”
Intel is exploring several other applications for silicon photonics, including networking. Outside of chips and other computer interconnects, it envisions potentially building lasers for the health care industry, the companys researchers said.
Ultimately, “if you build it, people will find ways to consume the bandwidth,” Paniccia said. “Were at the infancy of a true revolution people have been talking about for 20 years.”
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