Technical white paper | AHCI and RAID on HP EliteDesk and EliteOne 800 Business PCs
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Table 1. Basic AHCI and RAID definitions
Acronym or term Description
PnP Plug and Play
RAID Redundant Array of Independent Disks.
ROM Read Only Memory.
SATA Serial ATA
Strip Set of data on a single hard drive in a RAID 0 volume.
Stripe Group of all strips going horizontally across all the hard drive members of a RAID volume.
UEFI
Unified Extensible Firmware Interface. Specification defining firmware (BIOS and/or option ROM) that
initializes hardware subsystems before the OS boot process.
Benefits of AHCI
AHCI provides several benefits:
• Elimination of master/slave handling
• Native Command Queuing (NCQ)
• Hot-plugging
AHCI mode eliminates the master/slave topology for cabling SATA hard drives. Hardware and software that emulate IDE still
have some limitations with the master/slave topology that came from the Parallel ATA (PATA) mass storage
implementation. With AHCI mode, there is no need to worry about cabling considerations, other than the boot drive should
be on the lowest numbered SATA port (dark blue connector). SATA ports are independent of each other and are not tied
together by master/slave relationship.
Native Command Queuing (NCQ) is technology that allows a SATA device to internally optimize the order of command
execution for increased performance. Commands sent to a NCQ-capable SATA device are placed in an internal queue where
they can be dynamically and intelligently re-ordered and tracked.
Hot-plugging is the ability to insert a SATA device into a running system and have the operating system recognize the
device. AHCI is required for eSATA hot-plug functionality. Refer to the “Using eSATA on HP Compaq Business PCs” white
paper for more information about eSATA hot-plugging.
BIOS / Software / Hardware Considerations
BIOS interface
SATA Emulation Mode
SATA emulation mode can be set in F10 Setup by selecting Storage > Storage Options > SATA Emulation. SATA emulation
mode is set to AHCI by default.
RAID SATA emulation mode includes AHCI functionality. Customers purchasing a RAID system do not need to make any
changes in F10 Setup.
BIOS Support for _GTF in ACPI Mode
The system BIOS supports the Get Task File (_GTF) ACPI control method while in AHCI mode. However, a Registry key is
required to enable the port(s).
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