Webopedia on Google+Webopedia on TwitterWebopedia on FacebookTech Bytes Blog
Main » TERM » T »

TCQ

Short for tagged command queuing, a method of processing requests from a host device to a hard drive that is storing the data requested. TCQ was first introduced with the SCSI-2 standard as a way to allow hard drives to accept multiple concurrent commands from a host PC. When commands arrive at the drive's buffer, they are tagged with an identifier and then reordered by the drive��s microprocessor to minimize the distance the drive's read head needs to move laterally along the platter looking for data. For example, if a command is looking for data in one section of the drive and a following queued command is looking for data in a neighboring area, the SCSI host adapter can reorder the commands to make the two occur sequentially. This is a different system than SCSI-1 or IDE/ATA, which will allow only a single command to be outstanding at a time to any device and processes requests serially.

Tagged command queuing also is called command queuing and reordering.

Also see What's Inside a Hard Drive? in the Did You Know . . . ? section of Webopedia.







TECH RESOURCES FROM OUR PARTNERS
LATEST ARTICLES
8 Agenda Apps to Help Students Stay Organized

Webopedia's student apps roundup will help you to better organize your class schedule and stay on top of assignments and homework. Read More »

List of Free Shorten URL Services

A URL shortener is a way to make a long Web address shorter. Try this list of free services. Read More »

Top 10 Tech Terms of 2015

The most popular Webopedia definitions of 2015. Read More »

STUDY GUIDES
The 7 Layers of the OSI Model

The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. Use this handy guide to compare... Read More »

Computer Architecture Study Guide

Webopedia's computer architecture study guide is an introduction to system design basics. It describes parts of a computer system and their... Read More »

What Are Network Topologies?

Network Topology refers to layout of a network. How different nodes in a network are connected to each other and how they communicate is... Read More »