Intel Thunderbolt bolts through data transfers

PC World - After a few years in development, Intel formally unveiled its next-generation data transfer interconnect. The new Thunderbolt standard represents a shift in the underlying technology--and a potential shift in how we can do things down the road.

Thunderbolt began as a project out of Intel Labs, and was originally conceived as an optical technology, with optics in the cable as well as the device host controllers. That technology was codenamed Light Peak, and debuted at the Intel Developer Forum in 2009. The idea, explains Jason Ziller, director of Thunderbolt planning and marketing, was to create a single cable that supported high-speed transfers and multiple protocols, to address the explosion of data storage thanks to high-definition video and other digital media formats.

As recently as CES 2011, though, manufacturers were not optimistic about Light Peak surfacing anytime soon. And then the rumors surfaced about Intel switching away from the optical connector.

Which brings us to the unveiling of Thunderbolt. Gone is the "light" of Light Peak, as Intel moved away from the all-optical approach, because the costs on the host controller side were still too high for their PC OEMs, this in spite of the prices having come down over the course of development. Instead, Light Peak morphed into Thunderbolt, a high-speed, dual-protocol interconnect which uses an electrical copper wire.

That wire, together with the Thunderbolt host controllers, can deliver up to a mind-boggling 10Gbps across Thunderbolt's two channels. Thunderbolt supports both the PCI Express (PCIe) and DisplayPort protocols. Intel says it chose PCI Express because of its flexibility; and it chose DisplayPort because it's optimized for use with PCs (however, you can use a connector to convert a Thunderbolt cable to HDMI).

Each wire carries two independent bidirectional channels, so that translates to a total of 40Gbps maximum. Bandwidth can be split across multiple devices, as Thunderbolt--like FireWire 800 before it--supports daisy-chaining, in this case up to 7 devices.

"We determined an electrical connector was possible by having an innovative cable design, and being able to do it in a more cost effective manner," says Ziller of the choice to ditch optical. "The electrical solution is less expensive because there's no electrical to optical transceiver."

The only thing lost by going to copper, he added, is the support for long wires; the copper cables are limited to 3 meters in length. For those who do need the extra length, though, longer optical wires will be available.

"We haven't abandoned the idea of a light connection," says Ziller. "We still believe optics is in our future, and it will be necessary in our future. We're still doing research and development into that." Electrical isn't dead yet, but it will reach a dead end.