'Over the CPU' fans?

[Magicthyse]

No, not the CPU fan itself - I'm talking about the large 'sucker-upper' fans that you can get on some cases, which suck air from directly above the processor area out of the case. For example, there's one (9cm fan) on my Suntek Vision case.

My question is, do these really provide extra cooling, or do they just stir up the air / screw up airflow inside the case?

 

[SuperPickle]

Most of the time, these fans are set to blow right on the CPU. This gives the HSF essentially fresh, outside air in which to cool your processor giving you cooler temps. Does it work?--well, just think that the air that comes in from the intake fan that most people have in the front of their case has to pass by a bunch of hot stuff just to get to your CPU. With the side fan, your HSF has the coldest air available in which to cool the processor. Works good. If your HSF is set to 'suck', and the side fan is also exhausting, it then expells the hottest air in the case (barring the PSU air). Also works good.