From owner-freebsd-questions@freebsd.org Fri Sep 11 14:01:54 2015 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 39CE3A00ED9 for ; Fri, 11 Sep 2015 14:01:54 +0000 (UTC) (envelope-from wam@hiwaay.net) Received: from fly.hiwaay.net (fly.hiwaay.net [216.180.54.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E49341A1B for ; Fri, 11 Sep 2015 14:01:53 +0000 (UTC) (envelope-from wam@hiwaay.net) Received: from kabini1.local (dynamic-216-186-222-143.knology.net [216.186.222.143] (may be forged)) (authenticated bits=0) by fly.hiwaay.net (8.13.8/8.13.8/fly) with ESMTP id t8BE1pIN024284 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NO) for ; Fri, 11 Sep 2015 09:01:52 -0500 Subject: Re: USB physical ports To: freebsd-questions@freebsd.org References: <55F1A507.70402@gmail.com> <55F2C335.3030304@gmail.com> <55F2C469.4030101@hiwaay.net> <4365924.Nes7SDDcRu@desk8.phess.net> From: "William A. Mahaffey III" Message-ID: <55F2DECF.6020308@hiwaay.net> Date: Fri, 11 Sep 2015 09:07:21 -0453.75 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <4365924.Nes7SDDcRu@desk8.phess.net> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Sep 2015 14:01:54 -0000 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.