A riser card, such as a peripheral component interconnect (PCI) card, attaches to a circuit board such as a mother board in a transverse orientation and has a first connector and a second connector attached to opposing sides of the card for receiving expansion cards. In one embodiment, the first connector is offset from the second connector with respect to an axis in the plane of the riser card. In another embodiment, the first and second connectors each have a first and last pin, and the first pin of the first card is opposite the first pin of the second connector. The riser card may mount one expansion board right side up, and the second board upside down. The first and second connectors can be female connectors which are each matable with a male connector on the corresponding expansion board, or can be card edge connectors. The expansion boards, when mated with the connectors, are substantially parallel to, but offset from the circuit board. Advantageously, the expansion boards consume less space in the housing by sharing a single riser card, and overall bus length may be substantially reduced between components in addition to providing additional, more open, or better channel space for cooling air flow. A preferred embodiment mounts centrally on a mother board, and provides two side channels for air flow cooling through the chassis of a rack-mounted web server data processor device.