A communications technique using spare bit-lanes to communicate changes in interface physical link layer bandwidth and/or active width provides for dynamic adjustment of power consumption of interface links without requiring a separate control path for exchanging the change information. One or more spare bit-lanes are used to communicate an indication of the operating frequency/active width change to the physical link layer of the remote side of the interface and an acknowledgement is sent back to provide complete handshaking of the operating characteristic change. The method can determine whether or not a spare bit-lane is available and prevent making the change if a spare bit-lane is not available until the interface is repaired and a spare bit-lane can then be used for communicating operating changes in operating frequency/active width.