CPU fan direction.

Hi, which way is better/more efficient. To have the CPU fan blowing down onto the cooling fins of the heatsink, or have it sucking heat from the cooling fins?

Thanks MG gurus.

 

No other way about it, blowing down is better. Period. .....

 

Actually CPU fans are intended to pull the heat off of the heatsink fins (pulls air across), to cool the CPU off. If you are blowing air down onto the heatsink fins, you are actually causing heat to get higher, and cause shortening of the life of the CPU and motherboard. Now on laptops, Fans will push the air down onto the CPU heatsink fins, but they are designed to vent the hot air out of the side of the case per design of the duct that laptop manufacturers have around the heatsink and fan.

 

Every factory CPU fan I've seen or installed from 486's thru P4's has blown down on the heatsink. If the fan pulled air from the heatsink it would be drawing that air in from the sides of the heatsink which would be warmer air simply because it is comming from very near the MB and all of it's hot components. Blowing on the heatsink is the only way that makes sense to me.

 

Read for your self Here... I have been overclocking for damn near 8 years now... I have tryed every trick in the book to keep my CPUs cool. "sucking" air off a heatsink simply doesnt help. The exception being if thares a shroud in place, and its designed that way from the manufacturer.

 

Hmm, 2 out of 3 say to blow down on the CPU, sounds reasonable to me. Oh, BTW ACE 256, the link you've included seems invalid, please try again. Thanks for all the help.

 

That would be true in Overclocking, especially if the heatsink is designed. Most OEM machines that I have worked on have ducting over the fan to help disperse the hot air out of the case, not allow it to sit inside.

This is a debate that can be tried ala "MythBusters" style, which would be interesting to know how the performance of different heatsinks perform with the direction of the fan either pushing or pulling air across the heatsink fins.

 

Sorry about the link try this .... Overclocked or otherwise it doesnt matter.. your still taking heat away form a CPU....I have tryed it with countless heatsinks with the same result. Blowing down is cooler.....

 

I dunno how you could argue with ACE on this one the only time I have seen one blowin up(i think it was) was on my dads HP because it has an air duct that carries the heat out through a back fan.

 

I am not arguing with him. It depends on the application, due to how the case was designed for moving heat away from the CPU, and the Heatsink design. Some heatsinks are made to have air pushed down on them to pull heat away, while others are made to have air pulled up through them to move heat off.

Problem with pushing air down onto a heatsink, is that if it is not designed for that application, you are actually causing a situation that may shorten the life of the CPU.

 

Seriously no offence, but can you show me a cooler where the fan is blowing up ??

 

Like I stated, it depends on the design. Majority of the aftermarket coolers will push the air down since that is how they are designed, but most of the cheaper fin type heatsinks that manufacturers use are designed to pull air across the fins in order to cool the processor, due to how the case is designed (allows air to be pulled across to move heat off of the processor).

This is not a argument as some have conceived, due to some belive that it has turned that way. It has been an interesting discussion, due to the fact that I totally agree with you on the fact that you have to look at the design of the heatsink. With processors designed faster nowdays, you will tend to see more "Push" designs on heatsinks, where as on most of the older processors, you saw a "Pull" design. Even on a lot of the 200mhz Pentiums, you did not even see a fan on them, due to the heatsinks where a "Radiant" design.

 

I have seen a p2 where it has a HUGE heatsing that was not attached to a fan but right next to the back case fan.

 

Pull design heatsink http://www.tweak3d.net/reviews/alphapep66/ "The first thing you’ll notice about the PEP66T (and the original PEP) is that air is forced horizontally through the heatsink. The fan is attached to the large shroud and by default, pulls air from the heatsink. Alpha is known to have its fans pull air away from its heatsinks rather than push air onto them. Because of their design, the PC heatsinks that Alpha produces perform better when air is pulled away. The shroud that is on all of Alpha’s heatsinks play a big role in this and without them, the pull method wouldn’t work very well."

 

Oh dont take it as a argument ... more like a spirited debate ... but yea i agree, for older CPUs (<P2 <K6-2) it dident realy matter as long as thare was air moving....but in newer, faster systems cooling is far more critical....[edit] exactly the shroud is the key w/o it its pointless

 

I think the reason the fans blow down is because it causes more air to contact the heatsink, think about it. if it is blowing straight down and coming out the fins more air will touch the heatsink. if it is blowing up it created a vaccum and most of the air is sucked up near the top of the heatsink so some of the air is kinda wasted.

 

Some of the older cases where bad about creating vacums inside of them, until manufacturers started learning a thing or two from overclockers. Of course you have to love the design that Apple used on the G5. How much of a better heatsink design could you of made then they did.