SERIAL ATA

Serial ATA

 Serial ATA (SATA) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives and optical drives. Serial ATA succeeded the older Parallel ATA (PATA) standard,[a]offering several advantages over the older interface: reduced cable size and cost (seven conductors instead of 40 or 80), native hot swapping, faster data transfer through higher signalling rates, and more efficient transfer through an (optional) I/O queuing protocol.

SATA host adapters and devices communicate via a high-speed serialcable over two pairs of conductors. In contrast, parallel ATA (theredesignation for the legacy ATA specifications) used a 16-bit wide data bus with many additional support and control signals, all operating at much lower frequency. To ensure backward compatibility with legacy ATA software and applications, SATA uses the same basic ATA andATAPI command sets as legacy ATA devices.

SATA has replaced parallel ATA in consumer desktop and laptop computers, and has largely replaced PATA in new embedded applications. SATA's market share in the desktop PC market was 99% in 2008.[2] PATA remains widely used in industrial and embedded applications that use CompactFlash (CF) storage, which is designed around the legacy PATA standard, even though the new CFast standard is based on SATA.[3][4]

Serial ATA industry compatibility specifications originate from the Serial ATA International Organization (SATA-IO). The SATA-IO group collaboratively creates, reviews, ratifies, and publishes the interoperability specifications, the test cases and plugfests. As with many other industry compatibility standards, the SATA content ownership is transferred to other industry bodies: primarily the INCITS T13 subcommittee ATA, the INCITS T10 subcommittee (SCSI), a subgroup of T10 responsible for Serial Attached SCSI (SAS). The remainder of this article will try to use the terminology and specifications of SATA-IO.

Contents

                1 Features

                1.1 Hotplug

                1.2 Advanced Host Controller Interface

                2 Revisions

                2.1 SATA revision 1.0 (1.5 Gbit/s, 150 MB/s)

                2.2 SATA revision 2.0 (3 Gbit/s, 300 MB/s)

                2.3 SATA revision 3.0 (6 Gbit/s, 600 MB/s)

                2.4 SATA revision 3.1

                2.5 SATA revision 3.2 (16 Gbit/s, 1969 MB/s)

                3 Cables, connectors, and ports

                3.1 Data connector

                3.2 Power connectors

                3.2.1 Standard connector

                3.2.2 Slimline connector

                3.2.3 Micro connector

                3.3 eSATA

                3.3.1 eSATAp

                3.3.2 Pre-standard implementations

                3.4 Mini-SATA (mSATA)

                3.5 SFF-8784 connector

                3.6 SATA Express

                3.7 M.2 (NGFF)

                4 Protocol

                4.1 Physical layer

                4.2 Link layer

                4.3 Transport layer

                5 Topology

                6 Backward and forward compatibility

                6.1 SATA and PATA

                6.2 SATA 1.5 Gbit/s and SATA 3 Gbit/s

                6.3 SATA 3 Gbit/s and SATA 6 Gbit/s

                6.4 SATA 1.5 Gbit/s and SATA 6 Gbit/s

                7 Comparison to other interfaces

                7.1 SATA and SCSI

                7.2 Comparison with other buses

                8 See also

                9 Notes

                10 References

                11 External links

Hotplug

The Serial ATA Spec includes logic for SATA device hotplugging. Devices and motherboards that meet the interoperability specification are capable of hot plugging.

Advanced Host Controller Interface

Advanced Host Controller Interface (AHCI) is an open host controller interface published and used by Intel, which has become a de factostandard. It allows the use of advanced features of SATA such ashotplug and native command queuing (NCQ). If AHCI is not enabled by the motherboard and chipset, SATA controllers typically operate in "IDE[5] emulation" mode, which does not allow access to device features not supported by the ATA/IDE standard.

Windows device drivers that are labeled as SATA are often running in IDE emulation mode unless they explicitly state that they are AHCI mode, in RAID mode, or a mode provided by a proprietary driver and command set that allowed access to SATA's advanced features before AHCI became popular. Modern versions of Microsoft Windows, Mac OS X, FreeBSD, Linux with version 2.6.19 onward,[6] as well as Solaris and OpenSolaris, include support for AHCI, but older operating systems such as Windows XP do not. Even in those instances, a proprietary driver may have been created for a specific chipset, such as Intel's.[7]

Revisions

SATA revision 1.0 (1.5 Gbit/s, 150 MB/s)

Revision 1.0a was released on January 7, 2003. First-generation SATA interfaces, now known as SATA 1.5 Gbit/s, communicate at a rate of 1.5 Gbit/s, and do not support Native Command Queuing (NCQ). Taking 8b/10b encodingoverhead into account, they have an actual uncoded transfer rate of 1.2 Gbit/s (150 MB/s). The theoretical burst throughput of SATA 1.5 Gbit/s is similar to that of PATA/133, but newer SATA devices offer enhancements such as NCQ, which improve performance in a multitasking environment.

During the initial period after SATA 1.5 Gbit/s finalization, adapter and drive manufacturers used a "bridge chip" to convert existing PATA designs for use with the SATA interface.[citation needed] Bridged drives have a SATA connector, may include either or both kinds of power connectors, and, in general, perform identically to their PATA equivalents. Most lack support for some SATA-specific features such as NCQ. Native SATA products quickly eclipsed bridged products with the introduction of the second generation of SATA drives.

As of April 2010 the fastest 10,000 RPM SATA mechanical hard disk drives could transfer data at maximum (not average) rates of up to 157 MB/s,[8] which is beyond the capabilities of the older PATA/133 specification and also exceeds a SATA 1.5 Gbit/s link.

SATA revision 2.0 (3 Gbit/s, 300 MB/s)

SATA revision 2.0 was released in April 2004, introducing Native Command Queuing (NCQ). It is backward compatible with SATA 1.5 Gbit/s.[9]

Second-generation SATA interfaces run with a native transfer rate of 3.0 Gbit/s that, when accounted for the 8b/10b encoding scheme, equals to the maximum uncoded transfer rate of 2.4 Gbit/s (300 MB/s). The theoretical burst throughput of the SATA revision 2.0, which is also known as the SATA 3 Gbit/s, doubles the throughput of SATA revision 1.0.

All SATA data cables meeting the SATA spec are rated for 3.0 Gbit/s and handle modern mechanical drives without any loss of sustained and burst data transfer performance. However, high-performance flash-based drives can exceed the SATA 3 Gbit/s transfer rate; this is addressed with the SATA 6 Gbit/s interoperability standard.

SATA revision 3.0 (6 Gbit/s, 600 MB/s)

Serial ATA International Organization (SATA-IO) presented the draft specification of SATA 6 Gbit/s physical layer in July 2008,[10] and ratified its physical layer specification on August 18, 2008.[11] The full 3.0 standard was released on May 27, 2009.[12]

Third-generation SATA interfaces run with a native transfer rate of 6.0 Gbit/s; taking 8b/10b encoding into account, the maximum uncoded transfer rate is 4.8 Gbit/s (600 MB/s). The theoretical burst throughput of SATA 6.0 Gbit/s is double that of SATA revision 2.0. It is backward compatible with SATA 3 Gbit/s.[9]

The SATA 3.0 specification contains the following changes:

•             6 Gbit/s for scalable performance

•             Continued compatibility with SAS, including SAS 6 Gbit/s. "A SAS domain may support attachment to and control of unmodified SATA devices connected directly into the SAS domain using the Serial ATA Tunneled Protocol (STP)" from the SATA_Revision_3_0_Gold specification.

•             Isochronous Native Command Queuing (NCQ) streaming command to enable isochronous quality of service data transfers for streaming digital content applications

•             An NCQ Management feature that helps optimize performance by enabling host processing and management of outstanding NCQ commands

•             Improved power management capabilities

•             A small low insertion force (LIF) connector for more compact 1.8-inch storage devices

•             A connector designed to accommodate 7 mm optical disk drives for thinner and lighter notebooks

•             Alignment with the INCITS ATA8-ACS standard

In general, the enhancements are aimed at improving quality of service for video streaming and high-priority interrupts. In addition, the standard continues to support distances up to one meter. The newer speeds may require higher power consumption for supporting chips, though improved process technologies and power management techniques may mitigate this. The later specification can use existing SATA cables and connectors, though it was reported in 2008 that some OEMs were expected to upgrade host connectors for the higher speeds.[13]

SATA revision 3.1

Released in July 2011, revision 3.1 introduced/changed these features:[14][15]

•             mSATA, SATA for solid-state drives in mobile computing devices, a PCI Express Mini Card-like connector that is electrically SATA.[16]

•             Zero-power optical disk drive, idle SATA optical drive draws no power.

•             Queued TRIM Command, improves solid-state drive performance.

•             Required Link Power Management, reduces overall system power demand of several SATA devices.

•             Hardware Control Features, enable host identification of device capabilities.

•             Universal Storage Module (USM), a new standard for cableless plug-in (slot) powered storage for consumer electronics devices.[17][18]

SATA revision 3.2 (16 Gbit/s, 1969 MB/s)

•             SATA Express specification defines an interface that combines both SATA and PCI Express buses, making it possible for legacy SATA and PCI Express storage devices to coexist; see the SATA Express section for a more detailed summary.[19][20]

•             SATA M.2 standard is a small form factor implementation of the SATA Express interface, with the addition of an internal USB 3.0 port; see the M.2 (NGFF) section for a more detailed summary.[21]

•             microSSD introduces a ball grid array electrical interface for miniaturized, embedded SATA storage.[22]

•             USM Slim reduces thickness of Universal Storage Module (USM) from 14.5 millimetres (0.57 inches) to 9 millimetres (0.35 inches).[23]

•             DevSleep enables lower power consumption for always-on devices while they are in low-power modes such asInstantGo (which is formerly known as Connected Standby).[24]

•             Hybrid Information allows higher performance for solid-state hybrid drives.[25][26]

Cables, connectors, and ports

2.5-inch SATA drive on top of a 3.5-inch SATA drive, close-up of data and power connectors

Connectors and cables present the most visible differences between SATA and parallel ATA drives. Unlike PATA, the same connectors are used on 3.5-inch (89 mm) SATA hard disks (for desktop and server computers) and 2.5-inch (64 mm) disks (for portable or small computers).[27]

Standard SATA connectors for both data and power have a conductor pitch of 1.27 mm (0.050 inches). Low insertion force is required to mate a SATA connector. A smaller mini-SATA or mSATA connector is used by smaller devices such as 1.8-inch SATA drives, some DVD and Blu-ray drives, and mini SSDs.[28]

A special eSATA connector is specified for external devices, and an optionally implemented provision for clips to hold internal connectors firmly in place. SATA drives may be plugged into SAS controllers and communicate on the same physical cable as native SAS disks, but SATA controllers cannot handle SAS disks.

Female SATA ports (on motherboards for example) are for use with SATA data cables that have locks or clips to prevent accidental unplugging. Some SATA cables have right- or left-angled connectors to ease connection to circuit boards.