When the data transmission speed progress, capacitance and impedance effect more obvious. A terminal of the signal crosstalk to adjacent terminals and affects the signal integrity. In addition, grounding capacitance of high-speed signal impedance is reduced, so that the signal attenuation. New serial PCI specification PCI Express, 2.5Gb, the maximum data transmission speed in each direction for 500MB, greatly improved a single connector that can transmit signals. The past, high-speed signal by coaxial cable and coaxial connector to control the impedance of the signal pathway. PCI Express uses a similar concept, each signal terminals are separated from each other. Differential signals can reach this purpose very well, because each differential signals on the side of the grounding pin, in order to reduce crosstalk.