Is my USB 2.0 device running at full speed?

Question

How can I tell if my USB flash drive is running at full USB 2.0 speed? Currently I'd just like to verify that the drive is plugged into a 480 Mbps port, but in the past I've been unsure if a given device was USB 2.0 or an older revision. I'd like a way to identify its capabilities other than testing read/write speed.

Answer 1

You could check out

lsusb -v

On my system I get for example this line (and much more information):

Port 6: 0000.0503 highspeed power enable connect

Alternatively you can issue a:

tail -f /var/log/kern.log

in one terminal and then plug in the USB flash drive. On my system I get for example this message:

Sep 15 22:10:40 foo kernel: [405279.750140] usb 2-2: new high speed USB device using ehci_hcd and address 24

ehci_hcd is the USB 2.0 controler module in the kernel (i.e. everything is ok, the USB 2.0 stick is used with the right speed).

Unless you get a follow up message like this:

Sep 15 22:15:25 foo kernel: [405564.451402] usb 6-2: not running at top speed; connect to a high speed hub

(in this case probably compatibility problem with a low quality USB 2.0 stick (Kensington), since the computer's USB port supports USB 2.0 high speed devices otherwise)

With a non USB 2.0 high speed stick I get this message:

Sep 15 22:15:25 foo kernel: [405564.300127] usb 6-2: new full speed USB device using uhci_hcd and address 4

If your user account does not have access to /var/log/kern.log (or another system dependent kernel log message file location), you could use the command dmesg as an alternative to display the contents of the kernel message buffer. The disadvantage of dmesg is just that it does print such nice time stamps and it does not have a follow output option.