A six-layer printed circuit card has first, third and sixth layers which are signal carrying layers for interconnecting various components forming a personal computer. The second and fifth layers are both ground plane layers and the fourth layer of the card is a voltage plane. The components on the printed circuit card include eight input/output (I/O) connectors J1 - J8 to which eight other cards controlling various I/O devices can be connected. Seven of the eight I/O connectors are interconnected to a conventional I/O bus. The eighth connector J8 is interconnected to some lines of the I/O bus and to some lines of the signal carrying layers which form an internal bus.