PWM

PWM stands for Pulse Width Modulation. This is a widely used method for regulating the spinning speed of electric engines. It has some advantages regarding voltage control, being the most remarkable those that keep the torque and prevent the waste of energy –unlike what happens, for example, when resistors for voltage control are used.

This principle is based on feeding the engine intermittently with more or less short pulses, depending on the required speed. It sounds simple and in fact, it is, but it needs a more complex circuit than a simple resistor, as in voltage control. However, the advantages outweigh the small expenses it may incur at the beginning.

This technology has been applied for some time in motherboards to control the spinning speed of fans, depending on the temperature level. Consequently, we would get a quieter environment, as the fans will spin at high speed whenever the temperature rises, and in normal working conditions, the fans will spin at lower speed, and thus, the noise emission will be controlled.

The PWM is configured from the motherboard’s BIOS, and it is easy to spot those motherboards that include it, since the CPU cooler socket has 4 pins instead of 3.    

In traditional fans, there are 3 cords: one connects to ground, the other is in charge of feeding (these two are necessary for the fan to spin), and the last one sends the signal that indicates the current working mode (RPM).

In PWM fans, there are also three cords that work similarly to traditional fans, but there is a fourth cord that sends pulses to the fan in order to change its speed.

Another great advantage of this method regarding the one that uses 3 cords is that it doesn’t require any software to work, as the BIOS will do all that is necessary. So we can forget about installing and configuring software -that belongs to the past

Unfortunately, most of the motherboards that include PWM technology to fan control only come with 1 socket for that purpose, being the rest 3 pin sockets. Therefore, it would be possible to control the CPU fan speed but not that of the other fans, which are going continue spinning as usual. Consequently, the advantages of PWM are overshadowed by the rest of the fans that keep on making noise.

The people from Arctic Cooling created a way to take advantage of the pulse signal the only 4 pin socket produces to control all the fans in the PC.
 

Its patented PST technology consists in including a PWM amplifier and a special cord system that allows the connection of up to 5 fans to be controlled by the same outlet of the motherboard.  Additionally, each fan includes a traditional 3 pin plug that can be plugged into the motherboard so as to know the speed of each of them.