An improved I/O device, such as an audio/video router, includes at least a motherboard, such as a matrix board, including a plurality of locating slots and a plurality of connectors located on the motherboard such that when the motherboard is mounted in the I/O device, the plurality of connectors are positioned horizontally across the I/O device. The I/O device further includes a plurality of input/output (I/O) cards, such as audio/video cards, each of the I/O cards including a locating slot and two I/O connectors. In an I/O device of the present invention, the locating slot of each of the I/O cards mates with a respective locating slot of the motherboard such that the two I/O connectors of each of the I/O cards vertically straddle a respective connector of the motherboard thus maximizing a number of inputs and outputs able to be provided in the rear of the I/O device.