(SATA3, or SATA 6GB/second, was developed by the Serial ATA International Organization under the Serial ATA Revision 3.0 specs.)
In the current market most consumer-grade computers use either the SATA or SATA2 interfaces. These interfaces offer throughput speeds of 1.5Gbps and 3Gbps, respectively, or 150MBps and 300MBps. Because of software and hardware overhead, the actual speed of most SATA hard drives is still less than 200MBps.
The new SATA3 interface will raise the top throughput of hard drive speeds by 200 percent which will hopefully increase the actual transfer speed of hard drives accordingly.
The new SATA3 interface will be backward compatible with the existing SATA and SATA2 interfaces and will share the same cables and connectors. SATA3 enhances power efficiency and improves native command queuing, an inherent features of SATA standard, to increase overall system performance and data transfer speeds.
SATA3 is still in the final phase of development and there aren't any actual products out yet. AMD said it would fully support the technology with a revision of its current 750 chipset and future chipsets.
Seagate estimates however that the first SATA3-based hard drive will be by the end of the year.