1.1 Introduction

Fans are an essential part of any computer. They exhaust heat from the Electronic components of a Computer. They can be seen mounted on places like,

1. CPU Heatsink
2. Rear, Front and Top of a Computer Cabinet
3. Graphics Card
4. Power Supply
5. Chipset (y tho?)

This is of course excluding fancy cooling methods like Water cooling which is outside the scope of this article.

1.2 Size

One of the specification of fans is the diameter of the fan. If a large fan (say 140mm) and a small fan (say 92mm) need to push the same amount of air, the smaller one needs to spin faster. Spinning faster –> More noise. This is undesirable and fans also has a limit to how fast they can spin. Do note that the cabinet should support large fans to be able to mount them.

Verdict : Large » Small

Recommendation : 120mm

1.3 Mode of Spin and Connector type

Fans are of 2 types. PWM and non-PWM (a.k.a ‘DC’ fans for legacy reasons),

1. PWM - Spin in pulses (turns on and off rapidly)
2. Non-PWM/DC - Continuous (doesn’t turn off)

PWM is efficient, offers fine control and can reach very slow speeds (therefore can be quieter during low load)

DC is basic, cheaper, can only change speeds by changing voltage meaning they cannot reach as slow speeds as PWM (there is a minimum voltage beyond which they stop) and doesn’t offer fine control. Because they are cheap, they are the ones that often comes free with Cabinets.

DC has 3-pin header while PWM has a 4-pin header. The additional pin is for Pulse Width Modulation (hence PWM). So DC fans can be connected to either 4-pin or 3-pin headers while PWM exclusively requires 4-pin to work.

Verdict : PWM »»> DC