For AHCI, this queue has a depth - the number of I/O requests that can be kept waiting to be serviced in a port queue - of 32 commands. Older OS versions require hardware-specific drivers to support AHCI.Īs a traditional storage protocol developed for hard drives and tape, AHCI was designed to manage a single storage request queue. Windows has a registry workaround that will allow AHCI to be enabled after the OS is installed. However, it isn't easy to switch the BIOS setting from IDE mode to AHCI once the OS is installed. SATA hard drives and solid-state drives (SSDs) offer several modes of operation: IDE, AHCI or RAID, which usually has AHCI enabled. 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. Older motherboards may have IDE mode enabled by default and would need to be switched to AHCI before the operating system (OS) is installed.ĪHCI is supported on Windows Vista and later versions of Windows Linux since version 2.6.19 OS X and various open source operating systems, such as OpenBSD, NetBSD and FreeBSD. Most motherboards have AHCI enabled by default in the Unified Extensible Firmware Interface ( UEFI) or BIOS. Version 1.3.1 is the most recent iteration of the AHCI specification. Companies in the group included AMD, Dell, Marvell, Maxtor, Microsoft, Red Hat, Seagate and StorageGear.ĪHCI was an important part of building momentum for SATA II technology, providing a standard controller interface that optimizes advanced SATA features that weren't available with the older Integrated Drive Electronics ( IDE) standard interface. The specification was developed by the AHCI Contributor Group, which was comprised of hardware, software and OEM vendors, and was chaired by Intel. The specification also provides a standard way to program SATA-AHCI adapters. In 2004, Intel released the AHCI specification to define the functional behavior and software interface of AHCI. These peripheral component interconnect (PCI )-class devices move data between system memory and SATA storage media. Stacey Peterson, Senior Managing EditorĪdvanced Host Controller Interface, or AHCI, is a technical standard for an interface that enables software to communicate with Serial ATA ( SATA) devices.

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