Nov 09, 2012

How well do passive CPU coolers work?

At times work sounds like we have a Blackhawk chopper getting ready to take off with all the cooling fans running. Ok, maybe I'm exaggerating. A little. But it is pretty noisy. I was thinking about tying out passive coolers (big heat sinky things) that rely on large surface area and passive heat transfer instead of moving large volumes of air. How effective are passive CPU coolers compared to traditional fan designs?

Here's a pretty good article that covers cooling methods.

Computer cooling

"Computer cooling is required to remove the waste heat produced by computer components, to keep components within permissible operating temperature limits.

Components that are susceptible to temporary malfunction or permanent failure if overheated include integrated circuits such as CPUs, chipset, graphics cards, and hard disk drives.
Components are often designed to generate as little heat as possible, and computers and operating systems may be designed to reduce power consumption and consequent heating according to workload, but more heat may still be produced than can be removed without attention to cooling. Use of heatsinks cooled by airflow reduces the temperature rise produced by a given amount of heat. Attention to patterns of airflow can prevent the development of hotspots. Computer fans are very widely used to reduce temperature by actively exhausting hot air. There are also more exotic and extreme techniques, such as liquid cooling.
Many computers are designed to sound an alarm or switch off if certain critical internal temperatures exceed a specified limit.

Cooling may be designed to reduce the ambient temperature within the case of a computer e.g. by exhausting hot air, or to cool a single component or small area (spot cooling). Components commonly individually cooled include the CPU, GPU and the northbridge chip."


They are not going to work as well as an active fan (or H2O, if appropriate).  They operate in a more or less enclosed environment, and even if they have sufficient surface are to radiate significant amount of heat, where is that heat going to go?  A fan pushes the air out of the case while drawing in new air, but you are going to have to depend on good ole thermodynamics to move that hot air with a passive cooler.  It's quiet, I'll give you that, but passive coolers can even result in performance penalties due to CPU heat issues.  Here is a review of a pretty good passive cooler, and it still has this weakness.  



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