Editing Advanced Host Controller Interface (section)

== Operating modes ==
Many SATA controllers offer selectable modes of operation: legacy [[AT Attachment|Parallel ATA]] emulation (more commonly called IDE Mode), standard AHCI mode (also known as Native Mode), or vendor-specific [[RAID]] (which generally enables AHCI in order to take advantage of its capabilities). Intel recommends choosing RAID mode on their [[motherboard]]s (which also enables AHCI) rather than AHCI/SATA mode for maximum flexibility.<ref name="intel">{{cite web |url=http://www.intel.com/support/chipsets/imsm/sb/CS-015988.htm |title=Intel Matrix Storage Technology - Changing and/or choosing Serial ATA Modes |publisher=Intel |access-date=2007-09-30}}</ref> Legacy mode is a software [[Backward compatibility|backward-compatibility]] mechanism intended to allow the SATA controller to run in legacy operating systems which are not SATA-aware or where a driver does not exist to make the operating system SATA-aware.

When a SATA controller is configured to operate in IDE Mode, the number of storage devices per controller is usually limited to four (two IDE channels, master device and slave device with up to two devices per channel), compared to the maximum of 32 devices/ports when configured in AHCI mode.<ref>{{cite web |url=http://www.bswd.com/pciide.pdf |title=PCI IDE Controller Specification 1.0 |publisher=Berg Software Design |access-date=2015-05-03 |archive-date=2015-08-14 |archive-url=https://web.archive.org/web/20150814174048/http://www.bswd.com/pciide.pdf |url-status=dead }}</ref><ref name=":0">{{cite web |url=http://www.intel.com/content/www/us/en/io/serial-ata/serial-ata-ahci-spec-rev1-3-1.html |title=Serial ATA AHCI: Specification, Rev. 1.3.1 |publisher=Intel Corp. |access-date=2015-05-03}}</ref> But the [[chipset]] SATA interfaces may emulate more than one "IDE controller" when configured in IDE Mode.