This is a question that our customer service representatives get asked almost every week and there is a reason why. While most people know what SATA is, it get’s quite confusing to differentiate between the different revisions of the interface, here is a quick explanation :
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.
Special note for specific 2009 iMacs, 2008-2010 MacBooks & 2008-2009 MacBook Pros.
We highly recommend the use of a SATA 2.0 (3Gb/s) SSD such as the OWC Mercury Electra 3G for the following Macs:
While a 6G SSD does function, it will only do so at SATA Revision 1.0 (1.5Gb/s, 150MB/s) speeds rather that the SATA Revision 2.0 (3.0Gb/s 300MB/s) speed the computer can deliver.
What about the future ?
SATA III is starting to show some limits now with the latest generation of Thunderbolt 2 (20Gb/s) is showing up everywhere. With the ongoing race against speed it seems that the next step for quicker storage will be towards PCI SSD that will allow us to get over the limitation of SATA connectors.