About The Sata Interface - Seagate ST4000VX000 Product Manual

1.1 About the SATA interface

The Serial ATA (SATA) 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, SATA makes the transition from parallel ATA easy by providing legacy software support. SATA was designed to
allow users to install a SATA host adapter and SATA disk drive in the current system and expect all of the existing
applications to work as normal.
The SATA interface connects each disk drive in a point-to-point configuration with the SATA host adapter. There is no
master/slave relationship with SATA devices like there is with parallel ATA. If two drives are attached on one SATA 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.
The host adapter may, optionally, emulate a master/slave environment to host software where two devices
on separate SATA ports are represented to host software as a Device 0 (master) and Device 1 (slave)
Note
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 SATA environment.
The SATA 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 SATA host adapter contains a set of registers that shadow the contents of the traditional device registers, referred to as
the Shadow Register Block. All SATA devices behave like Device 0 devices. For additional information about how SATA
emulates parallel ATA, refer to the "Serial ATA International Organization: Serial ATA Revision 3.0. " The specification can be
downloaded from www.sata-io.org.
Seagate NAS HDD and NAS +SRS HDD Product Manual, Rev. E
Introduction
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