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New Spec Released for SATA Devices

A broad industry group is giving life to advanced features in Serial ATA II thanks to a new specification released this week.

Intel Tuesday released the Advanced Host Controller Interface (AHCI) v1.0 final specification and license agreement.

The spec was developed by the AHCI Contributor Group, a group of more than 40 members including Intel, AMD, Dell, Marvell, Maxtor, Microsoft, Red Hat, Seagate and StorageGear.

"Originally, we got a request from Microsoft to help synergize Serial ATA II like we did with USB2 and help the industry from a kind of adoptive standpoint," Thomas Loza, Intel technology initiatives manager told internetnews.com. "Standardizing on the interface makes it easier than non-controller specs and lets OS [operating system] providers like Microsoft write one driver set."

Serial ATA II is an enhancement spec of Serial ATA, which will be used to connect such internal storage devices as hard disks, DVDs and CD-R/Ws to the motherboard in desktop and mobile PCs, cost-sensitive servers and networked storage.

Intel said the features are expected to build on the momentum of Serial ATA version 1.0 in those hardware peripherals. The Serial ATA 1.0 spec was released in August 2001, and the final Serial ATA II enhancement spec was announced in October 2002.

AHCI describes a PCI class device that acts as an interface between system memory and SATA devices. According to the Contributor Group spec sheet, their host devices (referred to as host bus adapters, or HBAs) may support from 1 to 32 ports.

An HBA must support ATA and ATAPI devices, and must support both the PIO and DMA protocols. The HBA may optionally support a command list on each port for overhead reduction, and to support SATA command queuing via the DMA Setup FIS protocol for each device of up to 32 entries. The HBA may optionally support 64-bit addressing.

"With NCQ, Serial ATA devices can provide sophisticated command reordering optimizations for multi-threaded applications previously only available with higher-end storage interfaces," said Mike Alexenko, senior director at hard drive manufacturer Maxtor, in a statement.

Loza said the spec release is the kick-off of a broad initiative and is expected to build on the momentum of the Serial ATA v.1.0 specification as early as this summer.

"You will start seeing controllers showing up in the market," he said. "For example, our next generation Grantsdale/Alderwood chipset will have this controller spec."

Loza said other chip vendors are expected to follow including discreet chip manufactures like Adaptec. Later this year, Linux vendors are expected to put out their drivers. Microsoft has already pledged support for an AHCI driver as part of its Longhorn release.

As the specification begins to mature, Loza said the Contributor Group will continue to review and update it as necessary.