# USB-3 xhci question



## YuryG (Jun 22, 2019)

I have an USB-3 flash stick. And a motherboard with USB3 ports. At first, when I've inserted the stick, it showed SUPER speed. After unmount-detach-attach cycle it became only HIGH speed (i.e. USB2). Haven't managed to notice any error messages in dmesg or anywhere. What could be a reason for the problem?
/amd64 11.3-PRERELEASE r347510


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## aragats (Jun 24, 2019)

Not a real answer:
Neither devices nor controllers follow USB standards for 100%, especially USB 3.x. All kinds of issues happen with any OS which support USB, in most cases they are not really noticeable to regular users.

Of course, maybe there is a real (known) bug in your case, and somebody may point to a solution/work-around.


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## YuryG (Jun 24, 2019)

aragats said:


> …in most cases they are not really noticeable to regular users.


Can't  say they are not noticable, if speed drops multiple times during reattachment.


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## aragats (Jun 24, 2019)

YuryG said:


> speed drops multiple times during reattachment.


The nominal speed, right? The flash memory is significantly slower than USB. In _sync_ mode it won't be noticeable, the _async_ mode is not used unless explicitly specified.


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## YuryG (Jun 24, 2019)

aragats said:


> The nominal speed, right? The flash memory is significantly slower than USB. In _sync_ mode it won't be noticeable, the _async_ mode is not used unless explicitly specified.


I am not sure, I've got what you mean about sync/ async.
I'd say real speed. Reading speed. 90 MB/s vs 35 MB/s. Three times. I'm not expecting tremendous writing speed from flash. But reading could be quite fast.


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## tingo (Jun 25, 2019)

are you using the same usb port(s) in both cases? (ie super and high speed). It is common for motherboards to have both usb 3 and usb 2 ports, connected to separate controllers.


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## YuryG (Jun 25, 2019)

tingo said:


> are you using the same usb port(s) in both cases? (ie super and high speed). It is common for motherboards to have both usb 3 and usb 2 ports, connected to separate controllers.


Of course, the same USB socket of a blue colour.


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