Odie said:
I didn't claim to be a guru - but then I suspect you are one of the
"gotta have SATA - wow - 150MB/sec transfer rate" twits.
Then you 'suspect' wrongly. I'm one of those "know what the heck it is
before run around screaming 'marketing hype'" twits.
NCQ has nothing to do with the interface data rate.
One of the limiting factors to hard drive performance is mechanical
positioning of the head. NCQ minimizes that by, first, allowing multiple
commands to be queued and then reordering them so seek times are reduced.
Simplified example.
Say the computer wants to read a sector on 1. an outer track, 2. on an
inner track, and 3. on a middle track. Currently, with 'one at a time'
requests the hard drive first seeks to the outer track, then to the inner,
and then back to the middle.
With NCQ the three commands are queued and reordered so the drive reads the
sector on the outer track and picks up the middle track sector on it's way
to the inner track for the originally second, but now third, read. Seek
time is cut by a third since the middle track was picked up 'on the way'
and the drive didn't have to go back half way across the disk to get it.
http://www.seagate.com/docs/pdf/whitepaper/D2c_tech_paper_intc-stx_sata_ncq.pdf
