Which way should a heatsink fan blow?

  AllThumbs 14:03 09 Mar 2006

Hi all

I've just stuck a new heatsink on my cpu and attached the fan, but before I start her up I was wondering if it mattered which way the fan blew. It's a vertical fit so it can either blow air down through the sink onto the cpu, or up away from the sink pulling away the hot air.

Which is right?

Or is there no right way?

  Softstag 14:10 09 Mar 2006

Blowing down is normal. There are a few that can be used the other way round, but blowing cold air on to the CPU is the way you should do it.

  Jak_1 14:11 09 Mar 2006

It is usual to blow down on to the CPU. That way cools the chip much faster and more efficiently than drawing heat away from it.

  Totally-braindead 14:18 09 Mar 2006

I must admit the only ones I've any experience of are the stock AMD ones that come with the retail CPU and they only fit one way and are preinstalled anyway. I would think that dragging the warm air away from the heatsink would be the norm but from what the others are saying perhaps I'm wrong.
Still think it should drag heat away from CPU heatsink but will be interested to see what the others say.

  AllThumbs 14:32 09 Mar 2006

thanks folks...this seems to be the net consensus though people have tried it both ways.

  keef66 14:36 09 Mar 2006

Softstag and Jak_1 are correct; it's normal, and more efficient in cooling terms, for the fan to blast air downwards through the heatsink. Several manufacturers claim this also helps to cool the components around the cpu socket.
If you got a heatsink with a fan it's usually preinstalled the right way round.

The trickiest bits about the replacement of a heatsink are getting the right amount of thermal paste in the right place, and for AMD processors, clipping the thing down securely.

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