Serial ATA (SATA, or IPA: is a computer bus technology primarily designed for transfer of data to and from hard disks and optical drives.
It was designed as a successor to the legacy Advanced Technology Attachment standard (ATA), and is expected to eventually replace the older technology (retroactively renamed Parallel ATA or PATA). Serial ATA adapters and devices communicate over a high-speed serial link.
Historic Information on the Interface.
SATA 1.5 Gbit/s
First-generation SATA interfaces, also known as SATA/150 or (erroneously) as SATA 1, communicate at a rate of 1.5 gigabits per second (Gbit/s). Taking into account 8b10b coding overhead, the actual uncoded transfer-rate is 1.2 Gbit/s, or 150 megabytes per second (MB/s). In actual operation, SATA/150 and PATA/133 are comparable in terms of their theoretical burst-throughput. However, newer SATA devices offer enhancements (such as native command queuing) to SATA's performance in a multitask environment.
During the initial period after SATA/150's finalization, both adapter and drive manufacturers used a "bridge chip" to convert existing designs with the PATA-interface to the SATA-interface. Bridged drives have a SATA connector, may include either or both kinds of power connectors, and generally perform identically to native drives. They generally lack support for some SATA-specific features (such as NCQ). Bridged products gradually gave way to native SATA products.
SATA 3.0 Gbit/s
Soon after SATA/150's introduction, a number of shortcomings in the original SATA were observed. First and foremost, at the application-level, SATA's operational model emulated PATA in that the interface could only handle 1 pending transaction at a time. SCSI disks have long benefited from the SCSI-interface's support for multiple outstanding requests, allowing the drive targets to re-order the requests to optimize response-time. Native command queuing (NCQ) adds this capability to SATA. NCQ is an optional feature, and may be used in both SATA 1.5 Gbit/s or SATA 3.0 Gbit/s devices.
First-generation SATA devices were scarcely faster than legacy parallel ATA/133 devices. So a 3 Gbit/s signaling rate was added to the Physical layer (PHY layer), effectively doubling data throughput from 150 MB/s to 300 MB/s. SATA/300's transfer rate is expected to satisfy drive throughput requirements for some time, as the fastest desktop hard disks barely saturate a SATA/150 link. This is why a SATA data cable rated for 1.5 Gbit/s will currently handle second generation, SATA 3.0 Gbit/s sustained and burst data transfers without any loss of performance.
Backward compatibility between SATA 1.5 Gbit/s controllers and SATA 3.0 Gbit/s devices was important, so SATA/300's autonegotiation sequence is designed to fallback to SATA/150 speed (1.5 Gbit/s rate) when in communication with such devices. In practice, some older SATA controllers do not properly implement SATA speed negotiation. Affected systems require user-intervention to manually set the SATA 3.0 Gbit/s peripherals to 1.5 Gbit/s mode, generally through the use of a jumper.  Known faulty chipsets include the VIA VT8237 and VT8237R south bridges, and the VIA VT6420 and VT6421L standalone SATA controllers.  SiS's 760 and 964 chipsets also initially exhibited this problem, though it can be rectified with an updated SATA controller ROM.
The 3.0 Gbit/s specification has been very widely referred to as “Serial ATA II” (“SATA II”), contrary to the wishes of the Serial ATA standards organization that authored it. The official website notes that SATA II was in fact that organization's name at the time, the SATA 3.0 Gbit/s specification being only one of many that the former SATA II defined, and suggests that “SATA 3.0 Gbit/s” be used instead. (The Serial ATA standards organization has since changed names, and is now “The Serial ATA International Organization”, abbreviated SATA-IO.) Most SATA drive and controller manufacturers also do not use the term “SATA II”.
SATA 3.0 Gbit/s is sometimes also referred to as SATA 3.0 or SATA/300, continuing the line of ATA/100, ATA/133 and SATA/150.
Standardized in mid-2004, eSATA defined separate cables, connectors, and revised electrical requirements for external applications:
SATA 150 and SATA 300
These Inerfaces both use a Standard L-Connectors.
Uses Standard I-Connectors.
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