Embodiments described herein provide a method for providing a compatible backplane operation mechanism for 2.5-gigabit Ethernet. A first input of data including a first sequence-ordered set in compliance with a first interface protocol is received from a medium access control (MAC) layer. The first input of data is encoded into four outputs of encoded data including a second sequence-ordered set in compliance with a second interface protocol. The first sequence-ordered set in a first form of a sequence code followed by three bytes of data is mapped to the second sequence-ordered set in a second form of consecutive units of the sequence code followed by an encoded data byte. The four parallel outputs of encoded data are serialized into a serial output. The serial output to a linking partner is transmitted on a physical layer of an Ethernet link at a speed specified in the second interface protocol.