Lots of newer cases locate the power supply below the motherboard instead of above it. Which is better for cooling? I was always of the idea that having the PSU above the mobo was a good idea because the heat generated by the PSU wouldn't rise and add to the heat being generated by the CPU and other components on the mobo. Am I wrong? Someone please break down the relative advantages and disadvantages.
Having the psu on the bottom of the case allows the intake fan to draw in cool air from outside the case rather the warm air in the case. Also the tops of the case can be used for venting the hot air out.
There are really three very good reasons for having the PSU on the bottom of the case. First and most overlooked is balance- it's the heaviest component and having it there makes the entire tower more stable. Second, it draws in cool air from outside the case instead of running on the heated air inside. That is a major factor in keeping the power supply running at peak efficiency. Lastly, it allows for better case fan placement, with the rear exhaust at the highest point, and top exhaust openings possible.