A user has connected a USB 3.0 device to a computer using a 3 ft (1m) USB 3.0 cable. However, instead of an expected data transfer rate of up to 5 Gb/s, the user notes a data transfer rate of no more than 450 Mb/s. What is the most probable reason for this lower than expected data transfer rate?

A user has connected a USB 3.0 device to a computer using a 3 ft (1m) USB 3.0 cable. However, instead of an expected data transfer rate of up to 5 Gb/s, the user notes a data transfer rate of no more than 450 Mb/s. What is the most probable reason for this lower than expected data transfer rate?

• The device was connected to a USB 2.0 port on the computer.
• The cable used exceeds the maximum length that allows USB 3.0 to transfer data at 5Gb/s.
• The device was connected to a USB 1.1 port on the computer.
• The USB 3.0 cable is faulty.

Explanation: USB 2.0 allows transmission speeds up to 480 Mb/s and USB 1.1 allows transmission rates of up to 12 Mb/s in full-speed mode. A transmission speed of 450 Mb/s would indicate that a USB 2.0 port was used on the computer because USB devices can only transfer data up to the maximum speed allowed by the specific port. The generally accepted maximum length of a USB 3.0 cable is 9.8 ft (3m) which is three times the length of the cable used in this example, so the cable length is acceptable for full USB 3.0 capability. If a USB cable is faulty then no data transfer at all is likely to occur.

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