Serial ATA Guide

What is Serial ATA (Advanced Technology Attachment)?

Serial ATA as the name suggests is a serial interface,  which has been specifically designed to eventually replace the older parallel ATA disk interface. A number of the industry's leading vendors have formed the Serial ATA Working Group to jointly  develop the SATA interface. The Serial ATA 1.0 specification was  first released in August 2001.

ATA is currently the standard interface for IDE hard  drives and can be found in almost all consumer PCs, as well as many  high end professional PCs. The current hard disk interface uses a  16-bit wide data bus to communicate. To do so involves using a wide  40-pin ribbon cable, (figure 1) the Serial ATA specification  specifies a thin, point-to-point connection, (figure 2) which allows  for easy cable routing, it also avoids master/slave combinations and  improves airflow due to it's small cable design profile.

40 Way IDE  Ribbon Cable (figure 1)	Serial  ATA Cable (figure 2)

Serial ATA boasts data transfer speeds of up to  1.5Gbits/sec (150MByte/sec) and is expected to rise to 3Gbits/sec  (300MByte/sec) in the near future. Rumours of speeds of up to  6Gbits/sec (600MByte/sec) are also in the news!  Many  motherboard manufacturers have been quick to introduce this new  technology, and are now incorporating the new interface as standard  on the latest motherboards.

Serial ATA currently supports legacy drivers for  Parallel ATA technology and OEMs will be able to deploy the new  technology using existing parallel ATA drivers. It's also expected  that some vendors will be providing bridges for Parallel-to-serial  conversion. For those wishing to take advantage of the added  benefits of Serial ATA then a range of add-in controller/raid cards  (figure 3) and IDE to Serial ATA adaptors (figure 4) are currently  available.

2  Port Serial ATA PCI Raid Card (figure 3)	Serial  ATA to Ultra  ATA-133 Adapter Card (figure  4)

How does Serial ATA  work?

As with all computer technologies the need for speed has become paramount. The Serial ATA interface is no exception to  this with speeds of up to 3Gbits/sec and greater being boasted. To  achieve this increase in speed the interface has undergone a  complete re-design and the once familiar 40 Way (80 wire) ribbon  cable has completely disappeared.

To overcome a number of problems, and to achieve this  high transfer rate, the Serial ATA interface was defined. The new  interface employs a high-speed differential pair signaling  technique, the data being transmitted over two separate pairs, and a  separate power connector (figure 5) supplies the power for the  device.