These peripheral component interconnect (PCI)-class apparatus move data between system memory and SATA storage websites.
In 2004, Intel released the AHCI specification to specify the operational behavior and applications interface of AHCI. The specification also provides a standard means to plan SATA-AHCI adapters.
The specification was developed from the AHCI Contributor Group, which was comprised of hardware, software and OEM vendors, and was chaired by Intel. Businesses in the group included AMD, Dell, Marvell, Maxtor, Microsoft, Red Hat, Seagate and StorageGear.
AHCI was an significant part building momentum for SATA II technology, providing a typical controller interface that optimizes advanced SATA features which weren't available with the elderly Integrated Drive Electronics (IDE) standard interface. Version 1.3.1 is the latest iteration of this AHCI specification.
How Sata AHCI functions Works
Many motherboards have AHCI enabled by default at the Unified Extensible Firmware Interface (UEFI) or BIOS. Older motherboards may have IDE mode enabled by default and would have to be switched to AHCI before the operating system (OS) is set up.
AHCI is supported on Windows Vista and later versions of Windows; Linux since version 2.6.19; OS X; and various open source operating systems, including OpenBSD, NetBSD and FreeBSD. While Windows Vista and Windows 7 include the AHCI driver, those OSes won't install AHCI if it's not enabled on the boot drive's controller.
SATA hard drives and solid-state drives (SSDs) offer several modes of operation: IDE, AHCI or RAID, which usually has AHCI enabled. However, it isn't easy to change the BIOS setting from IDE style to AHCI once the OS is set up. Windows has a registry workaround which will allow AHCI to be enabled after the OS is installed. Older OS versions need hardware-specific drivers to encourage AHCI.
As a conventional storage protocol designed for hard drives and tape, AHCI was designed to handle one storage request queue. For AHCI, this queue includes a thickness -- the number of I/O asks that may be kept waiting to be flashed at a port queue -- of 32 commands.
Benefits and drawbacks of AHCI
AHCI enables advanced SATA features, including hot flashes and Native Command Queuing (NCQ). Hot swapping enables SATA drives to be switched out without having to shut the computer down.
NCQ optimizes how SSDs and hard drives handle simultaneous requests for information, minimizing the motion of the read-write heads and speeding up access time on hard drives with AHCI. On SSDs, NCQ boosts the performance of large file transfers.
One drawback to Sata AHCI Controller Driver Windows 7 is high latency if it is used with SSDs because the specification was developed for rotating storage media and not flash. Also, AHCI's restricted queue depth means the amount of I/O asks can easily become a bottleneck. Additional management must avoid having I/O requests neglect because they exceed the queue depth.
Because it was especially created for SSDs, NVMe is much quicker compared to AHCI, reduces latency and supplies better IOPS. Specifically, NVMe significantly increases the amount of I/O queues potential with queue depths of up to 65,000.