An apparatus electrically interconnects pins that project from the rear side of a backplane in separate arrays corresponding to respective circuit boards at the front side of the backplane. The apparatus comprises a connector board assembly extending across the rear side of the backplane between separate arrays of pins. The connector board assembly has signal routing circuitry that electrically interconnects those separate arrays of pins. This enables the respective printed circuit boards to be electrically interconnected independently of any signal routing circuitry within the structure of the backplane. Accordingly, the apparatus preferably includes a backplane that is free of signal routing circuitry for interconnecting pins that extend through the backplane.