In a method and apparatus for changing data transfer widths in a computer system, a first agent on a bus provides a first indication to a second agent on the bus identifying one or more data transfer widths supported by the first agent. The second agent then provides a second indication to the first agent identifying one or more data transfer widths supported by the second agent. A data transfer width is then determined based on the first indication and the second indication. According to an embodiment of the present invention, a third agent involved in a transaction is also able to provide a third indication to the first and/or second agents identifying one or more data transfer widths supported by the third agent. The data transfer width(s) is then determined based on the first, second, and third indications.