I wrote this article back in 2005 when the Athlon XP was current. It’s very outdated, but some of the basic concepts still apply. I’ve left it here as a historical artifact in the hopes that someone finds the information useful…

Fans & Ducts
So what’s all this about ducts you ask? There’s a basic problem with the way almost all HSF units are made. The fan is mounted directly on top of the fins of the heatsink. So, you say, what’s the big deal? The problem with this is the hub, or center of the fan.

The hub on most fans is at least 1/3 the diameter of the entire fan. Since it sits directly on top of the heatsink, this creates a dead spot, and right at the point where it’s the hottest, the center. Inserting a duct between the fan and the heatsink reduces the pressure and gets rid of the dead spot. This allows more even cooling across the entire heatsink.

So, now we have a more efficient heatsink. That’s great, but I need to knock off more than a couple of degrees celsius. In comes the Vantec Tornado. An average 80mm case fan will push anywhere from 20-35 CFM. (Cubic Feet [of air] per-Min) The tornado boasts up to 100 CFM! That’s a lot of air!! There is a catch however, at full speed this fan sounds like a jet engine. Since I don’t need the full cooling force of this monster most of the time, I’m using the CoolerMaster Aerogate II fan controller to reduce it’s speed (and noise) to a tolerable level. My heatsink is a Vantec model CCK-6040H (the high-speed noisy version) which is an all copper HSF with a 60mm fan that spins at 6800RPM and moves nearly 37 CFM. Not bad to start, but it’s not enough to take my AthlonXP 2500+ up to 2.2Ghz (3200+) and keep it cool enough to make me comfortable. (like I said.. I’m conservative..)

With the addition of a 60mm to 80mm funnel, the 45 degree angle duct and the Tornado fan I’ve knocked off 10 degrees celsius, and that’s at the unit’s lowest speed (~3200 RPM). Increasing the speed results in an immediate reduction in heat, and would probably allow this chip to be pushed a little harder. We’ll see, maybe I’ll get the guts to go a little higher. For now, here are a few post-op pics of the new and improved HSF…