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


We made some basic benchmarking using a NCQ-capable Serial ATA hard disk drive (Seagate ST3160023AS, 160 GB) with PC using the following configuration: 3.2 GHz Pentium 4, 1 GB RAM, GeForce 6800 VGA and Intel motherboard. We ran two programs, PCMark04 and IOMeter, with NCQ disabled and then enabled.

The results achieved with PCMark04 were the following: HDD Usage increased from 5,978 MB/s to 6,112 MB/s, an increase of only 2.24%. Windows XP loading time performance (XP startup) improved 9.76%, jumping from 8,947 MB/s to 9,821 MB/s.

The hard disk performance with IOMeter with NCQ disabled was 119 (a proprietary unit), jumping to 142 when we enabled NCQ, a 19.32% performance improvement. Not bad at all.

The performance difference between IOMeter and PCMark04 is easily explained. NCQ feature only improves the hard disk drive performance when it receives a series of out-of-order commands. It was very likeable that PCMark04 hard disk performance benchmarking used a series of sequential – i.e., in-order – commands, while IOMeter used a random workload, hence the better results on this program. Notice how Windows XP loading time – which loads files stored in several different positions of the hard drive – measured by PCMark04 improved considerably.

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Author: Gabriel Torres

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.

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