A rack-mount computer system includes one or more rows of computer racks, wherein each row of computer racks includes a pair of rows of computer racks positioned back-to-back relative to each other, a plurality of computer motherboards mounted in each of the racks in each row of computer racks and having front edges open to a workspace for receiving circulating air over the motherboards, the motherboards positioned to create a warm air plenum near a back edge of each motherboard, and a fan positioned adjacent each of the plurality of computer motherboards to circulate air across the computer motherboards and into the warm air plenum.