Many SATA controllers can enable AHCI either separately or in conjunction with RAID support. The specification details a system memory structure for computer hardware vendors in order to transfer data between system memory and the device.
The first pushes the 12th floor button and the second the 2nd floor.
It would be counterproductive to go to the 12th floor and then to the 2nd floor.
With Intel’s platform, the most important gains due to AHCI are noted with the Samsung, Maxtor and Seagate drives.
With NVIDIA it’s mainly the Raptor 150 GB and Samsung.
The principle of NCQ was already in the ATA norm since 1997 with TCQ (Tagged Command Queuing).
This heavier protocol could sometimes lead to significant performance losses in the case of low loads (no or very little command reorganisation to do) and has been integrated in a limited number of controllers.
Older operating systems require drivers written by the host bus adapter vendor in order to support AHCI.
Their claims might correct at certain extent, but it is hard to prove that those single threaded benchmark will reflect real world application.
AHCI is a hardware mechanism that allows software to communicate with Serial ATA (SATA) devices (such as host bus adapters) that are designed to offer features not offered by Parallel ATA (PATA) controllers, such as hot-plugging and native command queuing (NCQ).
Net BSD also supports drivers in AHCI mode out of the box in certain versions.