USB physical ports

William A. Mahaffey III wam at
Fri Sep 11 14:01:54 UTC 2015

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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