Most desktop storage systems today use a parallel bus interface referred to as Ultra ATA/100. The parallel ATA interface has been in use on desktop systems as the mainstream internal storage inter-connect since the 1980s (over 15 years!). Today's PCs demand higher speeds, more robust data integrity and flexibility for innovative smaller designs. Physically and electrically, the current parallel bus has run into limitations that will prevent this bus from providing higher data transfer speeds. The move to a new technology is inevitable in the eyes of industry leaders such as Intel, Dell, Seagate(r) and APT.

These same leaders formed the Serial ATA Working Group (serialata.org) and are dedicated to bringing this new technology to the forefront of today's PCs. Serial ATA is designed to overcome the limitations of parallel ATA while providing scalability for years to come. Setting the goal to be compatible and at cost parity with current parallel ATA drives when in volume, the Serial ATA Working Group is promoting the adoption of Serial ATA in all systems where ATA drives are being used today.

Serial ATA is a "serial" architecture as opposed to today's "parallel" ATA internal disc drive bus. Serial ATA wraps many bits of data into a packet and then at a higher speed (30 times faster) than parallel, transfers the packet of data down the wire to or from the host. In parallel drives today, Cyclic Redundancy Checking (CRC) is performed on the data being transmitted back and forth-but is not performed on the commands. Serial ATA integrates CRC on both the command and data packet level for enhanced bus reliability. Cyclic redundancy code detects all single and double-bit errors and ensures detection of 99.998% of all possible errors. A Serial ATA drive can transfer data at 150 Mbytes/sec on the bus to the host system with extremely reliable accuracy and the Serial ATA interface will continue to allow scalability for a very long time.

Serial ATA provides expansion for reliable performance growth

Additional Benefits

Serial ATA, an innovative new interface, allows continued performance growth, enhanced data reliability, and overall improved system dynamics above and beyond what parallel can efficiently continue to provide. Still in its early market-entry stage, Serial ATA provides immediate benefits to desktop users.

In addition to a faster, more reliable bus, Serial ATA improves cabling and connectors for a robust yet simpler integration. Gone are the days of bent pins, clumsy cabling and needlessly returned hard drives. Serial ATA cables are thinner and longer for improved system airflow and innovative system designs such as small form factor and consumer electronics boxes. Connectors are easier to snap into place in a "blind-mate" fashion, without any pins. Without the wide cables, system integrators can easily route the longer data cables (1 meter) within the system for simplicity or innovative designs.

The true Seagate "native" Serial ATA solution offers customers the "real McCoy" in Serial ATA technology. By implementing Serial ATA technology not only on the physical layer of the drive but also in the controller, Seagate drives can communicate directly from the drive to the host-up to the full 150-Mbytes/sec speed on the bus. In addition, the native solution incorporates command queuing, which can be a big performance boost in operating systems that can take advantage of that type of function. Some drive manufacturers may not immediately offer these "native" Serial ATA features on their first-generation Serial ATA drives.

Native Serial ATA = 150-Mbytes/sec bus speed, command queuing support, superset feature ready (for example, first party DMA)-A True Serial ATA Controller, Not Just a Translator Bridge Chip

An alternate way to quickly integrate Serial ATA onto a drive is to use a "bridge" solution: the drive manufacturer inserts a data serializer/de-serializer function before the data is sent or received by the on-board ATA controller. Data on a bridged Serial ATA solution can only be sent or received as fast as the ATA controller works. Since the serial functionality is not natively tied to the drive controller link and transport layers but is a separate function that translates data for a parallel controller, it can only transfer at the parallel controller's speed-100 or 133 Mbytes/sec.

The industry is ready to adopt Serial ATA technology, and Seagate will offer its customers a high performance, true native Serial ATA solution in the fall of 2002. Leading vendors will offer controller cards in the fall of 2002 and motherboards with Serial ATA ports integrated in mid-2003.