This is about heat, blowers and noise


PC cooling can be a noisy affair; a *performance* PC needs cooling for the following parts, and that can mean a lot of blowers:
- Power supply
- CPU
- north/south bridge
- graphics card
- harddisk
- evt. RAM


PC blowers can have 2, 3 or 4 pins.

type pin1 pin2 pin3 pin4
2-pin gnd +12V . .
3-pin gnd +12V sense .
4-pin gnd +12V sense control
colour black yellow green blue
alt.colour black red yellow blue

2: The speed of a 2-pin blower can be controlled by varying the voltage anywhere between 5 and 12V, or by switching the 12V on/off and varying the dutycycle (also called Pulse Width Modulation, PWM) between 20 and 100%.
3: The 3rd pin of a 3-pin blower is a 'sense' output that gives 2 pulses for each fan revolution, which is used to give feedback about fan speed.
The speed is controlled with PWM, which must be slow in order to be ON for a time that is long enough for the feedback to operate. That can result in irritating sound.
4: A 4-pin blower is an improved version of the 3-pin. Here the 12V is always ON, and the PWM is applied to the 4th pin (0 to 5V 'control' pulse).
The PWM speed is here normally 25kHz, which is a frequency above what humans can hear.




Here below are some good practical ways to increase cooling and reduce the noise:

Blower Control.
If you are looking for a circuit that automatically makes your cabinet fans running at the lowest speed, while keeping the temperature down, pls check this.
You can easily build it yourself. see here


Power Supply cooling.
Here you need a Power supply with a big but slow blower.
I previously often used a NorthQ 4001 400W PSU with 120mm fan (this is both good, quiet and cheap), but
now mostly use Corsair quality power supplies.  see here


Graphics card cooling. (updated 2019)

#1 The best you can buy is a graphics card with "passive cooling".
That means that it doesnt have its own blower, but is cooled with a large heatsink and airflow from other blowers in the PC cabinet.
Those blowers are normally big and with low speed, so they dont make so much noise but still move a lot of air.
But you need to have a good airflow through the passive heatsink!
Here below you can see how it can go wrong, and 2 ways to fix it. Click on the pictures to see the descriptions.
 
how to improve passive cooler airflow changing to newer generation GPU


#2 The second best is a graphics card with a big heatsink and slow blower mounted in it.

very quiet 2-slot ATI R9800


#3 Normally, if you have a Graphics card with blower, it has a very little heatsink and the blower is a fast-running noisy little fellow. It has only a limited lifetime, and then it starts screeking.
Of course you can mount a new little blower, but that is not so clever.
Here below you can see 2 better ways of fixing your graphics card cooling. Click on the pictures to see how to do it.

mount a bigger and quieter blower mount a passive heatsink cooler instead