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.

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