What is Native Command Queuing?
Q: What is Native Command Queuing?
A: Native Command Queuing (NCQ) is a technology designed to increase the performance of SATA hard disks on computers by allowing the individual hard disk to optimize the order in which it executes read and write requests.
Q: How does NCQ improve performance?
A: NCQ can reduce the amount of unnecessary drive head movement, resulting in better performance and slightly decreased wear of the drive for workloads where multiple read/write requests are outstanding at the same time, such as server-type applications.
Q: Does NCQ slow down HD access in certain applications?
A: Yes, NCQ can actually slow down HD access in certain applications like games and sequential reads and writes due to added latency induced by NCQ logic.
Q: How does Native Command Queuing differ from PATA TCQ?
A: Unlike PATA TCQ, command re-ordering with NCQ is performed by the drive rather than the operating system, and each command is equal in importance. The drive has more knowledge of its performance characteristics so it can take rotational position into account when optimizing commands. Additionally, NCQ has a maximum queue length of 32 compared to PATA TCQ's maximum queue length of 32 (31 in practice).
Q: What hardware requirements must be met for NCQ to be enabled?
A: For NCQ to be enabled, it must be supported and enabled both on the SATA host bus adapter and on the hard drive itself. Additionally, an appropriate device driver must be loaded into the operating system to enable NCq onthe host bus adapter.
Q: Is there generic AHCI support available for Windows XP?
A: No, Windows XP requires installation of a vendor-specific driver even if AHCI is present onthe host bus adapter. However Windows Vista includes a generic AHCI driver that allows generic support for AHCI devices.
