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USB 3.0 controller spec revealed

Posted: 19 Aug 2008 ?? ?Print Version ?Bookmark and Share

Keywords:USB 3.0? chip controller spec? draft xHCI?

Intel Corp. has released a nearly complete specification for a USB 3.0 controller chip. The Extensible Host Controller Interface (xHCI) draft version 0.9 aims to enable interoperable silicon for the so-called SuperSpeed USB interface that can deliver data rates up to 300Mbps at the application level.

Intel said it plans to release a revised xHCI 0.95 specification in the fourth quarter. Initially, Intel had aimed to finish the USB 3.0 spec early this year.

The current and future specs will be released under a royalty-free licensing agreement.

The computer giant has helped enable previous generations of the USB interconnect with its host controller designs because they set a gold standard for device interoperability. Over time the host controllers typically become embedded in Intel chip sets used on millions of PCs.

Reports circulated earlier this summer that other PC chip companies, including Intel archrival Advanced Micro Devices and Nvidia were concerned about delays getting the specs. Some representatives of the companies went so far as to suggest they might define their own USB 3.0 host controllers.

As part of the version 0.9 release, a number of companies including AMD, Dell, Microsoft and NEC expressed support for the Intel spec.

"USB 3.0 is an answer to the future bandwidth need of the PC platform," said Phil Eisler, general manager of AMD's chip set group in the Intel press statement. "AMD believes strongly in open industry standards, and therefore is supporting a common xHCI specification."

"Dell welcomes the availability of Intel's xHCI specification because it provides a single interface standard that will expedite the industry transition to next-generation USB 3.0," said Rick Schuckle, a client architecture strategist at Dell.

"Microsoft intends to deliver Windows support for hardware that is compliant with the xHCI specification," said Chuck Chan, general manager of Windows Core OS at Microsoft.

"NEC Electronics will now provide USB 3.0 solutions based on Intel's xHCI specification," said Hiroshi Iguchi, a vice president at NEC Electronics.

Intel announced in September 2007 it was working with Hewlett-Packard, Microsoft, NEC, NXP and Texas Instruments on the USB 3.0 spec, aiming at a theoretical performance of up to 4Gbit/s at the physical layer. At the time the group said it hoped to finish the basic spec in early 2008 and see first silicon implementing it emerge in early 2009.

The spec is a significant leap up from today's USB 2.0 which has a maximum of 480Mbit/s. It requires a new physical layer using two channels to separate data transmissions and acknowledgements to hit its higher speed targets.

In place of the polling and broadcast mechanisms used in USB today, the new spec will employ a packet-routing technique and only allow data transmissions when end devices have data to send. The new link also will support multiple flows per device and is capable of maintaining separate priority levels for each flow.

Proponents said USB 3.0 could supplant Firewire which they said is losing backing from companies such as Sony who have switched to USB 2.0 for products such as camcorders.

Nevertheless, USB 3.0 has its challenges in areas such as maintaining anything close to the five-meter reach of USB 2.0 and keeping costs low giving the additional routing work silicon must handle.

Separately, Intel confirmed it will support a new remote wake-up feature in some of its future motherboards that will let PC come out of a sleep state to receive a voice over IP Internet phone call. The feature will be available on four consumer motherboards initially. Intel is working with a handful of software and service companies to enable services that use the feature.

- Rick Merritt
EE Times

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