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

Adam Vande More amvandemore at gmail.com
Mon Jul 23 01:20:06 UTC 2012

On Sun, Jul 22, 2012 at 6:05 PM, Jakub Lach <jakub_lach at mailplus.pl> wrote:

> Speaking of misunderstanding, that's certainly
> possible.
> How much overhead is "normal" and alternatively,
> why in FreeBSD USB 2.0 reports as "40MB/s" and
> not other arbitrary number.

The overhead includes many different things including hardware latency.
 However the big one is USB communication itself.  That is static, you
can't change it and it doesn't vary(assuming same communication type).
 Your reported speeds are typical, and in all likelihood would be very
similar under another OS.

Adam Vande More

More information about the freebsd-questions mailing list