Serial ATA - It's Time to Get in Line


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Originally Published: 10/15/02
Most Recent Revision: 09/08/03

Serial Advanced Technology Attachment (SATA) is the hottest technology being developed for desktop storage and low end server drives today. Serial ATA is the next generation personal computer (PC) storage interface. It replaces the Ultra ATA/100 interface (otherwise known as the latest-generation Parallel ATA interface) — which is used to connect most PCs to their primary storage, and which has now become a bottleneck because it has reached its maximum burst data transfer rate speed of 100 MB/sec.

Serial ATA, on the other hand, has a burst data transfer rate speed of 150 MB/sec in its initial iteration and is expected to double in speed roughly every three years — to 300 MB/sec in 2004, 600 MB/sec in 2007, and so on.

This article describes the primary benefits of the Serial ATA interface and the increase in data rate. It also includes an explanation of why this technology is needed, what the advantages are, the possible impact on the storage environment, and the possible barriers to implementation. Other features and benefits are also outlined, together with a comparison to alternative storage interfaces.

What Is Serial ATA?

Serial ATA (Advanced Technology Architecture) is an interface used to connect hard drives and other peripherals to a PC. It is the evolutionary replacement for the Parallel ATA (PATA) physical storage interface.

In other words, Serial ATA is a storage interface specification for the next-generation computing platform. This interface will be used to connect storage devices such as hard disc drives, DVDs, and CD-R/Ws to the motherboard and is the replacement for today's Parallel ATA physical storage interface.

Serial ATA technology allows for platform cost reductions and performance improvements while supporting a seamless transition from Parallel ATA technology. Serial ATA supplies storage interface headroom, beginning with 1.5 Gbps and scaling to 2x, 4x, and beyond. At the same time, Serial ATA is a drop-in solution that is compatible with existing ATA software drivers and runs on standard operating systems without modification. It provides for systems that are easier to design, with narrower cables that are simple to route and install, smaller cable connectors, improved silicon design, and lower voltages, which alleviate current design constraints in Parallel ATA. Configuration of Serial ATA storage devices is much simpler, with many of today's requirements for jumpers and settings no longer needed.

Serial ATA is 100% software compatible with today's ATA, but has a much lower pin count, enabling thinner, more flexible cables. Serial ATA's cables can be up to a meter in length, and are small and neat because they only need seven conductors or a seven-pin data connector. Even the polarity-keyed plug is just eight millimeters wide. Contrast this with parallel ATA, which uses a 40-pin connector. APT Technologies, Quantum, Dell, IBM, Intel, Maxtor, and Seagate are jointly leading this initiative, with broad industry support from nearly 300 companies that make up the Serial ATA Working Group.

The Serial ATA Working Group

The Serial ATA Working Group is an industry organization whose mission is to define, develop, and deliver the industry specification for the Serial ATA interface. The Serial ATA Working Group is comprised of two groups:

  • First, the Serial ATA 1.0 Working Group was established in February, 2000 to specify Serial ATA for desktop applications. Since that time, the organization has grown several-fold and now totals over 200 members.

  • Second, the Serial ATA II Working Group was formed in February, 2002, to further address the needs of servers and networked storage market segments, and to specify next generation transfer speeds. The Serial ATA II Working Group is made up of over 86 members.

Page 2: The Need for Change

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