During the Computex conference, several motherboards equipped with a SATA 6 Gbps controller were already shown. This third-generation SATA interface has twice the bandwidth of its predecessor, a feature that should certainly come in handy with the next generation of solid state drives. Initially, ASUS and Gigabyte planned to implement the new SATA standard on its P55 and X58 motherboards.
Shamefully, problems started to surface with Marvell's S88SE9123 controller, resulting in cancellation of the plans. As of yet, ASUS has decided to use a different SATA 6 Gbps controller; the PLX8613 by PLX Technology. Because it's already to add the new controller to every P55 motherboard, ASUS will offer the SATA 6 Gbps functionality on a seperate expansion card. This card, as shown below, uses a PCI-Express 4x interface, providing enough bandwidth for two SATA 6 Gbps devices.
Because only few people will use the SATA 6 Gbps functionality, ASUS will sell the card seperately, rather than bundling it with its motherboards. The new controllerchip is still relatively expensive, though ASUS has not yet released any information regarding the price of the expansion card. Users that wish to have the PLX controller integrated on the motherboard could also purchase ASUS' high-end P7P55D Premium motherboard.
To show the performance increase of the new SATA generation, the motherboard manufacturer has run tests with a SATA 6 Gbps version of Seagate's ST3500410AS hard disk. In the benchmark HD Tach, the disk reached a 'burst speed' of 285,1 MB/s on the SATA 6 Gbps interface, compared to 185,9 MB/s on the current SATA 3 Gbps connector. As of yet, there are no interesting SATA 6 Gbps devices available for the regular consumer market, but it's quite likely that adding the controllers already will bring change to that.

ASUS launches SATA 6 Gbps controller for PCI-Express