[Discussion] What Is AHCI?

[Thomas Clayton]

I'm glad you asked that.

from:
http://forums.pcper.com/showthread.php?t=444831
"
AHCI (Advanced Host Controller Interface) is present on newer Intel chipsets such as 975X (ICH7), P965 (ICH8), and P35 (ICH9). AHCI mode is enabled in the BIOS and 3 settings are commonly available: IDE, AHCI, and RAID. The last two (AHCI and RAID) require a driver floppy and the F6 method when installing Windows XP otherwise the hard disks won't be 
detected.
"

but let's "use the source" as Linux fans would say.

THE specification(S)(?) are available, as PDFs, here.

http://www.intel.com/technology/serialata/ahci.htm

  (Daniela Engelhart, I hope knows this already.)
  (Also, I hope I've spelled her name correctly!)
"
AHCI Specification
	
Advanced Host Controller Interface specification for Serial ATA
 
The Advanced Host Controller Interface (AHCI) specification describes the register-level interface for a Host Controller for Serial ATA. The specification includes a description of the hardware/software interface between system software and the host controller hardware. This specification is intended for hardware component designers, system builders and device driver (software) developers.

Implementation of the Advanced Host Controller Interface Specification requires a license from Intel. ...

...

The latest revision of the specification is Revision 1.3. Subsequent Revision 1.x levels of the specification will be completed by Intel at its discretion as time and circumstances permit.
"


OR, every(?)body's favorite  'Every Person's "Encyclopedia"'

http://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface
"
The Advanced Host Controller Interface (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. The specification details a system memory structure for computer hardware vendors in order to transfer data between system memory and the device. As of June 2008, the current version of the specification is v1.3.[1]

Many SATA controllers can enable AHCI either separately or in conjunction with RAID support. Intel recommends choosing RAID mode on their motherboards (which also enables AHCI) rather than the plain AHCI/SATA mode for maximum flexibility, due to the issues caused when the mode is switched once an operating system has already been installed.[2]

AHCI is fully supported out of the box for Microsoft Windows Vista and the Linux operating system from kernel 2.6.19.[3] NetBSD also supports drivers in AHCI mode out of the box in certain versions. OpenBSD has had an ahci driver since OpenBSD 4.1. FreeBSD supports AHCI as well.
 ...
[***]
Older operating systems require drivers written by the host bus adapter vendor in order to support AHCI.
[***]
"

The first
http://forums.pcper.com/showthread.php?t=444831
 and 
this last 
http://forums.pcper.com/showthread.php?t=444760
URL are discussions of /using/ AHCI on Windows (XP and Vista). Some clues as to AHCI enabling and DISabling in the BIOS are given as well.


Sincerely,

Thomas Clayton

Now back to helping Ira Saxe.