News & Analysis

Serial ATA doubles data rate to 6 Gbits/s

Rick Merritt

8/18/2008 1:33 PM EDT

SAN JOSE, Calif. — The serial ATA interface is doubling its maximum data rate to support transfers up to 6 Gbits/second. The group marshalling the spec has also started a logo program to help ensure interoperability among the expanding group of hard, optical and solid-state drives using the link.

The Serial ATA International Organization (SATA-IO) officially ratified its physical layer specification for 6 Gbit SATA which should be posted at its Web site soon. The full SATA version 3.0 standard should be available before the end of the year.

"There is a need for the higher speeds in aggregation systems and elsewhere," said Knut Grimsrud, president of SATA-IO and an Intel fellow. "For instance some solid-state drive makers will be bumping up against the limits of the current 3 Gbit/s SATA interface with their next-generation products," he said.

The version 3.0 spec will also include a handful of extensions to its command set, especially in the area of data and command queuing. The enhancements are generally aimed at improving quality of service for video streaming and high priority interrupts.

The 6 Gbit/s SATA spec will continue to support distances up to a meter. The new speeds may require higher power consumption for supporting chips, factors that new process technologies and power management techniques are expected to mitigate. The spec can use existing SATA cables and connectors, although some OEMs are expected to upgrade host connectors for the higher speeds.

A new logo program will be an addition to an existing compliance testing program managed by SATA-IO. "We haven't had too much trouble with interoperability, but the range of SATA devices has been growing," said

Initially SATA was used by the handful of companies producing mainstream disk drives. Today a growing number of optical and flash drive makers are adopting the interface.

More than 650 million SATA hard disk drives shipped since its introduction in 2001, according to John Rydning, a research director at International Data Corp. Virtually all desktop and notebook computers and about a third of PC servers will use SATA drives by this year, according to IDC. High-end servers tend to use the Serial Attached SCSI or Fibre Channel interfaces for their greater flexibility and reliability.

At the chip-level, backers of the Open NAND Flash Interface continue to evolve their specification. At the Flash Memory Summit last week, proponent Micron showed a chip using two ports running at 166 MegaTransfers/second each and compliant with the ONFI 2.0 spec.

The group aims to upgrade the spec to a version 2.1 that will support up to 200 MT/s before the end of the year. Early next year it expects to launch a 3.0 effort that could double the data rate.

ONFI has contributed its specification to the Jedec standards group. A resulting Jedec committee aims to define a standard next-generation interface for flash chips that could be compatible with ONFI. However, the committee will need to reconcile the ONFI spec with interfaces used by flash giants Samsung and Toshiba, an effort that could take as long as two years, according to one source close to the effort.

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