Various circuit boards and systems are disclosed. In one aspect a system includes a circuit board and n differential signal via pairs. Each of the n differential signal via pairs has a first signal via and a second signal via and an electrical wall between the first signal via and the second signal via. There is a midline between every two adjacent differential via pairs. There are n ground return path vias. Each of the n ground return path vias is positioned substantially along one of the midlines and not on one of the electrical walls.