HP Compaq 515 Notebook-PC - Manual (Page 13)

4 Intel Matrix Storage Manager features
The Intel Matrix Storage Manager supports the following features.
Advanced Host Controller Interface
The Advanced Host Controller Interface (AHCI) is a specification that allows the storage driver to enable
advanced SATA features such as Native Command Queuing and hot plug capability. AHCI must be
enabled in the system BIOS for these features to apply (see
Enable RAID through the system BIOS
(f10) on page 12 ). AHCI is enabled by default on supported HP Business notebook PCs.
Native Command Queuing
A read/write drive head writes data to an HDD platter in concentric circles (tracks) based on the order
in which the write request was received. Because applications rarely request data in the same order
that it was written to the platter, long delays (latency) would result if the drive head had to locate data
in the exact order that the HDD receives read requests. Native Command Queuing (NCQ) allows SATA
HDDs to accept multiple commands and change their execution order to improve performance. This is
analogous to the way an elevator reorders floor requests to minimize travel time and mechanical wear.
Similarly, NCQ reduces the latency and unnecessary drive head movement required to execute multiple
outstanding read/write requests, resulting in increased performance and reliability. NCQ requires
support from the system BIOS, SATA controller, and controller driver.
Hot plug capability
Hot plug capability allows the SATA recovery HDD to be removed or inserted while the notebook PC is
running. Hot plug capability is supported when the recovery HDD is connected to the eSATA port or
located in the docking station SATA swappable bay. For example, the recovery HDD in the docking
station SATA swappable bay can be removed while the notebook PC is running if you need to temporarily
insert an optical drive in the bay. Hot plug capability also allows you to dock and undock the computer
at any time.
Advanced Host Controller Interface 9