Serial ATA II approaches--slowly

As the first serial ATA hard drives begin arriving in force, the group that developed the spec is already looking to its next generation, which adds features for workstations and servers.

The Serial ATA Working Group announced the Serial ATA II Port Multiplier 1.0 spec at the Windows Hardware Engineering Conference (WinHEC). The technology will permit future ports to host up to 15 drives.

The technology will most benefit servers, which will be able to run multiple rack-mounted hard drives off of one or two Serial ATA II ports on the motherboard.

Part Two

The Port Multiplier spec is the second in a group of technologies, or Serial ATA II extensions, that collectively will define the next generation of serial ATA. The first such extension, for native command queuing, was announced earlier this year. It will give hard drives the capability to prioritize data requests by multiple processors, in order to maximize throughput--an important enhancement for low-end servers and high-end workstations.

The Serial ATA Working Group continues to hammer out other Serial ATA II extensions. Some of the new functions will double the spec's bandwidth, from 1.5GB per second to 3GB per second. Others will specify failover switches, for use in situations where high reliability is vital. Still others will provide for connections of external Serial ATA II drives.

The entire series of Serial ATA extensions should be finalized "around midyear," according to Knut Grimsrud, an Intel senior principal engineer who chairs the Serial ATA Working Group. In the meantime, vendors are free to create Serial ATA 1.0 products that incorporate any or all of the extensions.

Serial ATA's Advantages

Serial ATA 1.0, introduced almost a year ago, represented a major advance in hard drive technology over the venerable parallel ATA that most computers used. Among other things, Serial ATA drives reduce in-case cable clutter because they connect to the motherboard with skinny 0.25-inch cables. Conventional parallel ATA drives use 2-inch ribbons. Serial ATA drives also consume less power than their predecessors.

PC World's tests suggest that most general business users who substitute Serial ATA for parallel ATA won't detect any speed advantage. But the extra bandwidth could make a difference for servers using RAID technology to operate multiple hard drives.

One factor delaying widespread adoption of Serial ATA is lack of system support. Right now, you have to install a PCI card and custom drivers to add Serial ATA ports to an older PC. But that may change: This week Intel also announced version 0.95 of the Advanced Host Controller Interface for Serial ATA.

This software allows systems to discover and implement Serial ATA features. Microsoft has said that the next version of Windows will include a driver for the interface.

Intel notes, however, that it's not clear when Windows XP's successor (code-named Longhorn) will appear. Microsoft this weekforecast a 2005 debut for that OS. Intel representatives say that the chip maker will complete the controller interface specification itself.

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Yardena Arar

PC World
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