SATA 6G is the next big drive transfer standard. As it stands right now Marvell is the only company with an available controller. Because of this we see them being hastily added to motherboards. In their first run the controllers failed to provide the anticipated performance and caused stability issues on the P55 boards they were placed on. These were quickly removed and the P55 was launched without SATA 6G.
However, the issue was and still is one of implementation. You see, the P55 Express chipset only has PCI-e Gen 1 lanes in it. All of the PCI-e Gen 2 lanes were moved to the Lynnfield CPU. This is normally okay as the only AIB (add in boards) that need this much bandwidth are graphics controllers. Not a problem, right? – Actually, it is a big problem. Read more at TweakTown.