usb 3.0 thumb drive speed limit

[Marat N.Afanasyev]

Gary Palmer wrote:
> On Mon, Jan 02, 2017 at 11:27:49AM +0300, Marat N.Afanasyev wrote:
>> I wonder is there a speed limit on usb 3.0? I've bought
>>
>> ugen0.4: <SanDisk> at usbus0
>> umass2 on uhub7
>> umass2: <SanDisk Extreme, class 0/0, rev 2.10/0.10, addr 4> on usbus0
>> da2 at umass-sim2 bus 2 scbus9 target 0 lun 0
>> da2: <SanDisk Extreme 0001> Removable Direct Access SPC-4 SCSI device
>> da2: Serial Number AA010808161609220143
>> da2: 40.000MB/s transfers
>> da2: 59840MB (122552320 512 byte sectors)
>> da2: quirks=0x2<NO_6_BYTE>
>>
>> that claims 'Up to 245 MBytes/sec read speed'
>
> I don't think the speed reported by the SCSI layer (CAM) is correct
> for USB, although it seems from an experiment here that if you
> plug a USB3 drive into a USB2 port it reports "40.000MB/s transfers"
> and on a USB3 port it reports "400.000MB/s transfers".  SCSI doesn't
> really have any direct mapping to the USB speeds so I suspect the
> USB stack uses the closest value.  The tests I did were with 10.3.
> Other releases may behave differently.
>
> Check with usbconfig what the negotiated USB speed is (the "spd=" value
> with the Mbps or Gbps value in brackets afterwards)
>
> FULL = USB1
> HIGH = USB2
> SUPER = USB3
>
> Regards,
>
> Gary
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it seems that drive doesn't attach as usb 3.0 even when plugged into 
pci-e card port directly, to say nothing about the hub. probably it's 
buggy firmware of addon card, I'll try to find newer firmware and flash 
it, if one exists

-- 
SY, Marat

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