Expansion boxes have been traditionally used to provide additional expansion slots to those that are provided in the computer system. As the speed of expansion busses has increased, it has become increasingly difficult to provide an expansion box and interconnect to that expansion box that is reliable and low cost. For example, PCI Express Gen 3 provides a very high speed interconnect, allowing data rates up to 32 GBytes/sec in some configurations. Various techniques to maintain the signal integrity of this expansion bus, even over distances greater than 1 meter, are disclosed. Some of these techniques include proper selection of cable impedance, proper selection of PC board materials, and specific PC layout guidelines.