On 15/04/2011 09:17, Xiaofan Chen wrote:
> On the other hand, even though I have bought two
> USB 3.0 external hard disks, none of my PCs
> come with USB 3.0 host controller (XHCI)

For Random Access, an HD might just beat USB 1.1

Only bursts to or from the on-board controller cache can exhaust the=20
speed of USB 2.0 on a single drive.

Drives are natively faster toward edge of platter. Native block transfer=20
sequential speed (excluding track to track stepping or random access) is=20
limited by rotational speed and bit density. For larger transfers, even=20
without Random Access, the track to track delay is very high.

USB 2 is worthwhile. I'm sceptical that USB 3.0 is needed for ordinary=20
single drives.
--=20
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