to save a bit of space and cost, i want to mount several (20?) APU2 vertically in a self-made chassis, so that they go side-by-side. The chassis will occupy 4U in a rack and be deep enough to accommodate the APU2 and a 140mm silent fan at least. From what i know, there are two holes on two sides of the cpu that could be used to mount a passive cooler. Any suggestions on which cooler to use and how to mount? Would that even provide enough cooling (thus the fan) under ambient conditions?