They are usually intended for servers, because they are all passively cooled. You need a lot of air moving through the card, so you need a system that was designed to support them. Putting one in a typical desktop would not be wise, because it would overheat. There are some actively cooled versions so you would have to be sure what you are purchasing. Look at this article for model numbers -- http://wccftech.com/xeon-phi-hpc-codenamed-knights-corner-revealed/