Abstract: A computer system housing where a vertical printed circuit board, e.g., a riser card, is inserted into a socket on a computer system motherboard. Some internal space within the housing may allow optimization of system memory capacity through packing of additional memory modules on the riser card. The additional memory may be mounted on the riser card and may reside in the vertical space created between the riser card and the directly-mounted memory on the motherboard. The computer system housing further includes a chassis that may be partitioned into two separate sub-chassis for proper positioning of one or more cooling fans as well as to accommodate changes in computer system configurations with minimized retooling of the chassis. The cooling fans may be mounted at such locations on the chassis that allow optimization of air circulation and, hence, cooling within the housing.