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Fans: Which way to blow?

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New Member
Jan 23, 2001
Hi there,

I was just wondering what is the "best" direction for a fan on a heatsink to blow. Is it better to pull heated air away from the heatsink or instead simply reverse the fan so that it blows air down through the heatsink?

I know heat rises so having the fan pull the air away from the heatsink is better but I've also heard that it is far easier to push something than it is to pull it; the same goes for air. So what do you guys recommend? Thanks in advance.
It depends on a lot of things. I have one machine with a PEP66 on a slotket and it works best exhausting from the heatsink. I have a dual cpu board and PEP66s with the shrouds turned for socket use and they are 2 degrees cooler blowing into the heatsink.

The only way to know for sure is to try it and see.
With the way heatsinks are made a fan blowing ON the heatsink is better. There is too much are in between the fan and heatsink base to effectively pull heat away from it. You would actually be pulling in air from outside the heatsink which would be a waste.

2C is a big difference.