A system and method for flexible multiple protocols are presented. A
device's logical layer may be dynamically configured on a per interface
basis to communicate with external devices in a coherent or a
non-coherent mode. In coherent mode, commands such as coherency protocol,
system commands, and snoop response pass from the device's internal
system bus to an external device, thereby creating a logical extension of
the devices internal system bus. In non-coherent mode, the input-output
bus unit receives commands from the internal system bus and generates
non-coherent input-output commands, which are eventually received by an
external device.