As a rule of thumb there are two types of CPU cooler on the market. The "conventional" and most common design which is a "Tower-Heatsink" design. This consists of one, two or sometimes three aluminium heatsink "towers" with fans in between them and they are generally quite tall - around 160mm. The second type of CPU cooler is a "Top-Down" style where there is normally a single aluminium heatsink which is positioned horizontally to reduce height. The "Top-Down" is reflective of the fact there is normally a fan at the top blowing downwards. Sometimes these types of cooler can equip two fans but normally there isn't enough space for a fan below. There are other coolers that won't fall into either of these categories, the No Fan CR-95C, and some that fall into both, the Prolimatech Genesis, but as a general rule these coolers are very rare.



Link: eTeknix