1. WHAT IS NATIVE COMMAND QUEUING, OR NCQ?
Command Queuing has long been a feature in SCSI technology, but it is just now making its way into the ATA storage world. Native Command Queuing is a technology designed to improve the performance of SATA hard drives by optimizing the execution order of read and write requests sent to them. A standard SATA drive without NCQ technology will execute commands as they are received, but a SATA NCQ drive's internal command queue will be reordered for optimal performance on the fly. To optimize performance, NCQ technology reorders the commands in such a way that reduces the amount of seek time the drive needs to access data. In other words, the NCQ reordering algorithms utilize such information as the physical location of the data on the disk. A common analogy for NCQ is the way an elevator works - it stops at near floors first rather than the order in which the buttons were pressed, thus reducing the total amount of time to meet all requests (drop everyone off at the floor they selected). Native Command Queuing has the most profound effect on performance in multi-tasking and applications with heavy asynchonous I/O loads. An added benefit of NCQ is that it will probably increase the lifespan of drives that use it since the amount mechanical movement for seeking is reduced.
One important thing to note about NCQ technology is that it requires not only a drive that supports it but also host-side support, meaning the PC that the drive is connected to must have a controller capable of using NCQ. Today, only Intel's 915 and 925 platforms with the Intel 82801FR I/O controller hub (ICH6R) have this feature.