Hard Disk and SSD Drives

SATA versions and backwards compatibility || How hard disk and SSD drives work

There are only three main standards used to interface a computer to internal hard disk drives, CD/DVD drives, etc. – the SCSI/SAS and IDE PATA standards – which have been available for many years, plus the latest standard called serial ATA, usually abbreviated to SATA. SATA is available in three versions – SATA 1.5 Gbit/s (the first version – SATA 1) and SATA 3.0 Gbit/s (the second version – SATA 2/SATA II) and SATA 6.0 Gbit/s (SATA 3). Two revisions of SATA 3 have taken place – SATA revisions 3.1 and 3.2.

SATA 3 and SATA 2 devices can run on an SATA 1 motherboard or adapter-card host controller, which is called backward compatibility. These three standards are also forward-compatible.

An SATA 1 drive will run on an SATA 3 controller, etc., but a drive using the earlier standard cannot run at the faster data-transfer speeds of a later version of the standard.

SATA versions and backwards compatibility –

Note that the full SATA 3.0 (SATA 6 Gbit/s) standard was released on May 27, 2009. Seagate says that SATA 3.0 is 100% faster than SATA 2.0 while being backward compatible with the existing SATA 2.0 standard with regard to cables, etc.

This is what used to be written on Seagate’s website: “The SATA 6-Gb/s interface enables the use of the industry’s newest and fastest hard drive controllers, while providing backward compatibility to legacy SATA 1.5-Gb/s or 3-Gb/s systems.”

The latest internal hard disk drives support the new SATA/600 (or SATA 3.2) standard which runs at a theoretical 6Gb/s. Just remember that most theoretical speeds are far from being achieved in practice.

Serial ATA [SATA] – “The new specification can use existing SATA cables and connectors, although some OEMs are expected to upgrade host connectors for the higher speeds. Also, the new standard is backwards compatible with SATA 3 Gbit/s [SATA 2].” –


Note that Gbit/s is gigabit per second, not gigabyte per second. There are 8 bits in a byte of information, so the latter speed is eight times faster than the former. 1.5 Gbit/s is equal to 150MB/s (megabytes per second) and 3.0 Gbit/s is equal to 300MB/s. Consequently, you may also see these two SATA standards described as SATA 150 and SATA 300.

Data rate units – http://en.wikipedia.org/wiki/Data_rate_units

Technical information on how hard disk and SSD drives work

If you want to know the technical details of how a hard disk drive and SSD works, click the relevant link.


How Solid-state Drives Work –