Abstract: The disclosed technology includes an assembly of two planar expansion card cards, which provides functionality to be leveraged by an upper planar expansion card. The base planar expansion card includes a first connector A, a first connector B, a connector C, a first pass-through connector A configured to connect to the first connector A, and a first pass-through connector B configured to connect to the first connector B. An upper planar expansion card includes a second connector A and a second connector B. The second connector A and the second connector B connect to the first pass-through connector A and the first B connector pass-through, respectively. In some implementations, the second connector A and second connector B are configured for a PCI-E and the connector C is configured for Ethernet KR signals.