AHCI: Difference between revisions

AHCI (Advance Host Controller Interface) is developed by Intel to facilitate handling SATA devices. The AHCI specification emphasizes that an AHCI controller (referred to as host bus adapter, or HBA) is designed to be a data movement engine between system memory and SATA devices. It encapsulates SATA devices and provides a standard PCI interface to the host. System designerdesigners can easily access SATA drives using system memory and memory mapped registers, without the needsneed tofor manipulating the annoying task files as IDE do.

An AHCI controller may support up to 32 ports which can attach different SATA devices such as a disk drivedrives, a port multipliermultipliers, or an enclosure management bridge. AHCI supports all native SATA features such as command queuequeueing, hot plugplugging, power management, etc. To a software developer, an AHCI controller is just a PCI device with bus master capability.

ComparingAHCI withis a new standard compared to IDE, which has been therearound for twenty years,. AHCIThere is a new standard and there areexists little documentsdocumentation about its programming tips and tricks. MaybePossibly the only available resource is the Intel AHCI specification (see [[#External Links|]External Links]]) and some open source operating systems such as linuxLinux. This article shows the minimal steps an OS (not BIOS) should do to put AHCI controller into a workable state, how to identify drives attached, and how to read physical sectors from a SATA disk. To keep concise, many technical details are omitted, as well asand deep explanations of some data structures have been omitted.

All the diagrams in this article are copied from the Intel AHCI specification 1.3.