Hardware Secrets posted an article on NCQ (Native Command Queuing) and TCQ (Tagged Command Queuing)

NCQ (Native Command Queuing) and TCQ (Tagged Command Queuing) are features created to improve the hard disk performance by re-ordering the commands sent by the computer to the hard disk drive. In this tutorial we will explain how both NCQ and TCQ work, the difference between them and some performance data.

NCQ (Native Command Queuing) and TCQ (Tagged Command Queuing) Explained