An integrated circuit to serialize local data and selectively merge it with serialized feed-through data into a serial data stream output that includes a parallel-in-serial-out (PISO) shift register, a multiplexer, and a transmitter. The PISO shift register serializes parallel data on a local data bus into serialized local data. The multiplexer selectively merges serialized local data and feed-through data into a serial data stream. The transmitter drives the serial data stream onto a serial data link. In another embodiment of the invention, a method for a memory module includes receiving an input serial data stream; merging local frames of data and feed-through frames of data together into an output serial data stream in response to a merge enable signal; and transmitting the output serial data stream on a northbound data output to a next memory module or a memory controller. Other embodiments of the invention are disclosed and claimed.