Abstract: A cooling system for a multi processor system mounted in a rack that has a top, a bottom, sides and a plurality of card cages. Each of the card cages has card guides for receiving mother boards such that the mother boards are positioned vertically within the rack. A CPU is mounted on a mother board and a heat sink is mounted on top of the CPU and fastened to the mother board. The heat sink includes a plurality of air passages and is positioned with respect to the mother board such that when the mother board is mounted in the rack, the air passages are vertical. A blower is integrated into the rack such that air flows vertically through the rack. Also a heat sink for use on a baby AT mother board on which a CPU socket is mounted and into which a CPU is plugged.