"da0: 40.000MB/s transfers" What was rationale behind pegging USB 2.0 at 40MB/s?

Adam Vande More amvandemore at gmail.com
Sun Jul 22 22:45:04 UTC 2012

On Sun, Jul 22, 2012 at 4:20 PM, Jakub Lach <jakub_lach at mailplus.pl> wrote:

> Hi,
> I was fortunate enough to buy USB 3.0 pendrive,
> which actually works with FreeBSD just ripped from
> package! (normal _empty_ FAT filesystem, no
> garbageware added, no need to format).
> It actually bounces from 40MB/s limit when reading
> from it.
> Writing is about 18MB/s.
> Device is supposed to be "467x" which should
> be about 70MB/s.
> And USB 2.0 hard limit is 60MB/s.
> Wouldn't be nice to squeeze few additional
> MB/s?

You are suffering a misunderstanding of how USB 2 works.  There is a lot of
overhead to it.  If you want USB 3 speeds, buy a USB 3 controller.
Adam Vande More

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