USB physical ports

[William A. Mahaffey III]

On 09/11/15 07:10, Ernie Luzar wrote:
> Patrick Hess wrote:
>> Ernie Luzar wrote:
>>> How can I confirm 480Mbps transfer rate.
>>
>> Run "dmesg -a" after plugging in the device. A USB 2.0 flash drive
>> should be reported with a 40 MB/s transfer rate:
>>
>>     da1: <Intenso Rainbow Line> Removable Direct Access SCSI-4 device 
>>     da1: 40.000MB/s transfers
>>
>> You can verify this by reading from the drive, e.g. by using dd(1):
>>
>>     # dd if=/dev/da1 of=/dev/zero bs=1M count=1024
>>     1024+0 records in
>>     1024+0 records out
>>     1073741824 bytes transferred in 52.099073 secs (20609615 bytes/sec)
>>
>> That's ~20 MB/s, definitely more than USB 1.x could have delivered.
>>
>
> Yes that is true, BUT it's a very long way from 480Mbps. Following are 
> some test results.
>
> Before plugging in flash drive
> /root/bin >usbconfig
> ugen3.1: <EHCI root HUB Intel> at usbus3, cfg=0 md=HOST spd=HIGH 
> (480Mbps) pwr=SAVE (0mA)
> ugen2.1: <UHCI root HUB Intel> at usbus2, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
> ugen1.1: <UHCI root HUB Intel> at usbus1, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
> ugen0.1: <UHCI root HUB Intel> at usbus0, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
>
> After plugging in flash drive
> /root/bin >usbconfig
> ugen3.1: <EHCI root HUB Intel> at usbus3, cfg=0 md=HOST spd=HIGH 
> (480Mbps) pwr=SAVE (0mA)
> ugen2.1: <UHCI root HUB Intel> at usbus2, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
> ugen1.1: <UHCI root HUB Intel> at usbus1, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
> ugen0.1: <UHCI root HUB Intel> at usbus0, cfg=0 md=HOST spd=FULL 
> (12Mbps) pwr=SAVE (0mA)
> ugen3.2: <Cruzer Blade SanDisk> at usbus3, cfg=0 md=HOST spd=HIGH 
> (480Mbps) pwr=ON (200mA)
>
> Get this result no matter which physical port I plug into.
>
> Get these console messages when plugging in flash drive
>
> umass0: <SanDisk Cruzer Blade, class 0/0, rev 2.00/1.27, addr 2> on 
> usbus3
> umass0:  SCSI over Bulk-Only; quirks = 0x8100
> umass0:2:0:-1: Attached to scbus2
> da0 at umass-sim0 bus 0 scbus2 target 0 lun 0
> da0: <SanDisk Cruzer Blade 1.27> Removable Direct Access SPC-4 SCSI 
> device
> da0: Serial Number 4C530001020404102235
> da0: 40.000MB/s transfers
> da0: 14907MB (30529536 512 byte sectors: 255H 63S/T 1900C)
> da0: quirks=0x2<NO_6_BYTE>
>
> Why is it saying 40.000MB/s transfers? Is this some max value that 
> Freebsd is limited to?
>
>
> /root/bin >dd if=/dev/da0 of=/dev/null bs=1M count=10
> 10+0 records in
> 10+0 records out
> 10485760 bytes transferred in 0.607835 secs (17250996 bytes/sec)
>
> /root/bin >dd if=/dev/da0 of=/dev/null bs=1M count=100
> 100+0 records in
> 100+0 records out
> 104857600 bytes transferred in 5.683069 secs (18450876 bytes/sec)
>
> /root/bin >dd if=/dev/da0 of=/dev/null bs=1M count=200
> 200+0 records in
> 200+0 records out
> 209715200 bytes transferred in 11.233349 secs (18668983 bytes/sec)
>
> /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.
>
> 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).

-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.