From owner-freebsd-questions@freebsd.org  Fri Sep 11 13:28:16 2015
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From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
To: Ernie Luzar <luzar722@gmail.com>
Cc: freebsd-questions@freebsd.org
Subject: Re: USB physical ports
References: <55F1A507.70402@gmail.com> <2091716.bhpPQfPjgk@amd.asgard.uk>
 <55F216CB.6040606@gmail.com> <2029052.xQsMmxkVaC@desk8.phess.net>
 <55F2C335.3030304@gmail.com>
Reply-To: freebsd-questions@freebsd.org
Date: Fri, 11 Sep 2015 09:28:01 -0400
In-Reply-To: <55F2C335.3030304@gmail.com> (Ernie Luzar's message of "Fri, 11
 Sep 2015 08:04:05 -0400")
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Ernie Luzar <luzar722@gmail.com> writes:

> /root/bin >dd if=/dev/da0 of=/dev/null bs=1M count=400
> 400+0 records in
> 400+0 records out
> 419430400 bytes transferred in 22.415176 secs (18711894 bytes/sec)
>
>
> If 20Mbps is the max rate Freebsd can do, then 18.7Mbps is a good rate.

You're confusing bits with bytes. 19 megabytes per second is (with
overhead) over 250 megabits per second, which is a bit over half of the
theoretical max for USB 2.0, but perfectly respectable for inexpensive
flash drives.

> But the real question is why is Freebsd USB rates capped at 20Mbps
> when the hardware says it's capable of 480Mbps?

The hardware is capable of transfers at 480 megabits per second, but
that doesn't mean that the flash can physically read data that quickly.