SATA is a hardware connection standard that provides data transfer between hard drives and a computer's motherboard. The current standard is SATA III as of December 2012; SATA I was supplanted by SATA II around 2006. SATA connectors have been the default way of connecting hard drives to motherboards since around 2004 The first SATA hard drives were released in 2003 and had significant performance increases.
The primary difference between SATA II and SATA II is the transfer speed, which is measured in gigabits per second. SATA II has a peak transfer rate of 3 Gbps, SATA III has a peak transfer rate of 6 Gbps. One Gbps is roughly 100 megabytes per second pulled from the drive.
Connectors and Cables
SATA ports on motherboards and the cables that connect hard drives use a different interface than the older IDE standard; this simplified assembling computers, and the cables are both less expensive and more durable. Regardless of the generation of SATA being used, the cables are identical and using an old SATA cable does not impact the data transfer speed.
Compatible Drives and Ports
If an SATA II device is plugged into a SATA III port, the port detects the slower device, and the data transfer rate is dialed down to match. To get maximum performance, always make sure that your hard drive's SATA generation matches the SATA ports on the motherboard of the computer you're building.
In 2010, the standards organization behind SATA broke away from using Roman numerals to designate SATA generations, and lists them by their transfer rates in Gbps. SATA II became SATA -- 3.0 gigabit -- and SATA III became SATA -- 6.0 gigabit.
What is the difference between SATA I, SATA II and SATA III?
SATA I (revision 1.x) interface, formally known as SATA 1.5Gb/s, is the first generation SATA interface running at 1.5 Gb/s. The bandwidth throughput, which is supported by the interface, is up to 150MB/s.
SATA II (revision 2.x) interface, formally known as SATA 3Gb/s, is a second generation SATA interface running at 3.0 Gb/s. The bandwidth throughput, which is supported by the interface, is up to 300MB/s.
SATA III (revision 3.x) interface, formally known as SATA 6Gb/s, is a third generation SATA interface running at 6.0Gb/s. The bandwidth throughput, which is supported by the interface, is up to 600MB/s. This interface is backwards compatible with SATA 3 Gb/s interface.
SATA II specifications provide backward compatibility to function on SATA I ports. SATA III specifications provide backward compatibility to function on SATA I and SATA II ports. However, the maximum speed of the drive will be slower due to the lower speed limitations of the port.
Example: SanDisk Extreme SSD, which supports SATA 6Gb/s interface and when connected to SATA 6Gb/s port, can reach up to 550/520MB/s sequential read and sequential write speed rates respectively. However, when the drive is connected to SATA 3 Gb/s port, it can reach up to 285/275MB/s sequential read and sequential write speed rates respectively.