When building a new homebrew computer system, most users concentrate on CPU speed, amount of RAM, how large of a hard disk they get, and the biggest and baddest video display adapter they can afford. But fans, as important as they are, are often overlooked. For those not building a water cooled system, fans, fan speed, and placement can determine how cool or not so cool your system will run.

CPU Fans
The selections are unlimited, as is the pricing. We normally assume that a higher priced unit will cool better than an el cheapo – which may or may not be true, depending on the brand. One brand that receives high marks is Zalman. But with any CPU fan you purchase, make sure that the fan and heatsink are going to fit your motherboard. There is nothing more disappointing than to have a CPU fan that will not fit because of something protruding from the mobo. Also, when installing a CPU fan, you should use thermal grease such as Artic Silver between the CPU and heatsink for better heat transfer. And thin is in. I’ve seen some people pile a blob on, which is a no-no. Some fans are heat controlled and will adjust fan speed upwards as temperatures climb.

Case fans come in a variety of sizes, and the case design will determine what size or sizes will fit inside of your case. Most cases will accommodate either 80mm or 120mm fans, which is fairly standard. Not standard are the power connectors, of which there are two types.

  • 4 prong connector. This type of connector plugs into your standard power supply connectors. They work well and also come in thermal controlled design.
  • 3 pin connector. This type of fan connects directly to the motherboard itself. Most motherboards will come with 3 or more 3 pin connectors depending on the design. The benefit is that you can observe temperatures from either the BIOS or 3rd party software, which some boards come with and/or control the speed of the fan.
  • And there are combo fans that provide the best of both worlds and come with both 4 prong and 3 pin connectors.

Fan placement, how many fans to use, and type of fans is somewhat of a black art, since case design and motherboard placement come into play. And there have been many studies, much debate, and a lack of consensus when it comes to fan placement. . So I’ll throw in my two cents. I normally start out with three fans. One CPU, which is always required, and two case fans, one at the front and one at the back. The front fan blows into the case, the rear fan blows air out. This, in combination with the power supply fan, usually will provide sufficient cooling.

However, test the system and see what your temps are. As stated, you can use the software that may have come with your motherboard or use third party software such as SpeedFan, which is free. Just remember your BIOS must support this feature and the fans need to be connected to the motherboard itself.

So what are normal temperatures? Here is a general guide you may wish to look at:

THE HEATSINK GUIDE: Maximum CPU temperature and maximum CPU power usage

Comments, as always, are welcome.

[tags]computer, software, build, fans, [/tags]