Date: Fri, 11 Sep 2015 09:07:21 -0453.75 From: "William A. Mahaffey III" <wam@hiwaay.net> To: freebsd-questions@freebsd.org Subject: Re: USB physical ports Message-ID: <55F2DECF.6020308@hiwaay.net> In-Reply-To: <4365924.Nes7SDDcRu@desk8.phess.net> References: <55F1A507.70402@gmail.com> <55F2C335.3030304@gmail.com> <55F2C469.4030101@hiwaay.net> <4365924.Nes7SDDcRu@desk8.phess.net>
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On 09/11/15 08:54, Patrick Hess wrote:
> William A. Mahaffey III wrote:
>> On 09/11/15 07:10, Ernie Luzar wrote:
>>> But the real question is why is Freebsd USB rates capped at 20Mbps
>>> when the hardware says it's capable of 480Mbps?
>> I think you are confusing bits & bytes. 480 Mbps = 60 MBps, lower case
>> 'b' is bits, upper case 'B' is bytes, 8b / B (8b per B).
> That's the first reason.
>
> In addition, just because the bus is capable of transmitting up
> to 480 Mb/s, that doesn't mean the devices connected to that bus
> will also be able to process data at that rate. As a matter of fact,
> most el-cheapo USB thumb drives won't. Try that again with a modern
> HDD or even an SSD and you'll get much better results.
>
> Patrick
Absolutely correct, I am usually happy w/ 1/2 - 2/3 of spec speed w/
*any* I/O operation.
--
William A. Mahaffey III
----------------------------------------------------------------------
"The M1 Garand is without doubt the finest implement of war
ever devised by man."
-- Gen. George S. Patton Jr.
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