A method and apparatus are provided for implementing a redundancy enhanced
differential signal interface. A differential signaling I/O pair is
coupled to a differential receiver interface. The differential receiver
interface includes a pair of multiplexers coupled to a differential
receiver. An error detecting mechanism is coupled to the differential
receiver for detecting an error. When an error is detected, an interface
operating speed is reduced. True and complement sides of a differential
signaling I/O pair are alternately tested by first enabling a multiplexer
control of one of the multiplexers, reading data, and checking for the
error; then enabling a multiplexer control of the other multiplexer,
reading data, and checking for the error. Responsive to detecting a
failure of a true side or a complement side, the detected failed true
side or complement side is set to a reference voltage and the reduced
interface operating speed is maintained for continued operation.