Bit rate

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Overview

Bit rate is a unit for denoting the speed of a data link between devices. The actual speed of the information transfer is a little slower since additional bits need to be inserted into the transferred data for technical reasons.

Specific bit rates

Some typical bit rates related to keyboard/computer protocols:

  • ADB: 0.010 MBit/s
  • PS/2: about 0.016 MBit/s
  • USB 1.0: 12 MBit/s
  • USB 2.0: 480 MBit/s
  • USB 3.0: 5000 MBit/s
  • USB 3.1: 10000 MBit/s

Baud rate

Bit rate and baud rate often get confused. The baud rate is the speed at which a signal changes its state. USB up to version 2.0 uses only two different states on the data line, the "J" and the "K" state. Hence, bit rate and baud rate have the same value for these. USB 3.0 and 3.1 use additional wire pairs that allow for more complex states, so that a single state change (or the absence of it) can encode several bits, resulting in a bit rate that is larger than the baud rate by the same factor.