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1.1
About the Serial ATA interface
The Serial ATA interface provides several advantages over the traditional (parallel) ATA interface. The primary advantages
include:
• Easy installation and configuration with true plug-and-play connectivity.
It is not necessary to set any jumpers or other configuration options.
• Thinner and more flexible cabling for improved enclosure airflow and ease of installation.
• Scalability to higher performance levels.
In addition, Serial ATA makes the transition from parallel ATA easy by providing legacy software support. Serial ATA was
designed to allow users to install a Serial ATA host adapter and Serial ATA disk drive in the current system and expect all
of the existing applications to work as normal.
The Serial ATA interface connects each disk drive in a point-to-point configuration with the Serial ATA host adapter. There
is no master/slave relationship with Serial ATA devices like there is with parallel ATA. If two drives are attached on one
Serial ATA host adapter, the host operating system views the two devices as if they were both "masters" on two separate
ports. This essentially means both drives behave as if they are Device 0 (master) devices.
NOTE
The Serial ATA host adapter and drive share the function of emulating parallel ATA device behavior to provide backward
compatibility with existing host systems and software. The Command and Control Block registers, PIO and DMA data
transfers, resets, and interrupts are all emulated.
The Serial ATA host adapter contains a set of registers that shadow the contents of the traditional device registers, referred
to as the Shadow Register Block. All Serial ATA devices behave like Device 0 devices. For additional information about
how Serial ATA emulates parallel ATA, refer to the "Serial ATA: High Speed Serialized AT Attachment" specification. The
specification can be downloaded from www.serialata.org.
Seagate Exos X24 SATA Product Manual, Rev. A (Draft 1)
The host adapter may, optionally, emulate a master/slave environment to host
software where two devices on separate Serial ATA ports are represented to host
software as a Device 0 (master) and Device 1 (slave) accessed at the same set of host
bus addresses. A host adapter that emulates a master/slave environment manages
two sets of shadow registers. This is not a typical Serial ATA environment.
Introduction
7
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