Key Takeaways
- PWM allows precise fan speed control without noticeable stops, regulating max RPM.
- Fan sizes and speeds impact noise output, with smaller fans typically being louder.
- PWM helps increase fan longevity, reduces noise, and maintains optimal PC temperatures.
PWM stands for Pulse Width Modulation, which is a type of signal used to control electronics. When it comes to PC fans, they run at a constant 12V, which never changes. However, PWM can turn the PC fans on and off so fast that you won’t even be able to notice, essentially regulating the speed of the fans.
Once started, the fans will have momentum, so it isn’t that they are completely stopping at any time, they will just slow down for something silly like 1/100th of a second then ramp back up. If you tell the fan to turn off and on an equal number of times, this would put the fan at 50% of its maximum RPM.
For instance, if you had a 2,000 RPM and you had the PWM turn the fan off 50% of the time and turn it on the other 50%, the fan would run at 1,000 RPM. The same would hold true if you told the 2,000 RPM fan to turn on 75% and turn off 25%, it would then run at 75% of its max speed which would be 1,500 RPM. This all seems quite simple and is essentially how PWM works, by controlling the power on and power off percentages.
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Do fan sizes and Min/Max speeds matter?
These factors have a big effect on what is going on inside your PC. All PWM fans will have a minimum and a maximum RPM (Revolutions Per Minute) which they can run at. In most cases, the smaller the fan, the higher the min/max RPM. For instance, a 90mm fan may have a minimum speed of 800 RPM and a max of 2,500 RPM. However, a 140mm fan may have a minimum speed of 400 RPM and a max of 1200 RPM.
With the size of the fan and its speed taken into account, there is also a direct correlation to the noise output from the fan. A smaller fan with a higher RPM is going to output much more noise than a bigger fan with a lower maximum RPM. When you remember that some 90mm fans can output almost twice as much RPM as 140mm fans, it starts to make sense as to why they are a bit louder when being used at max speeds.
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Why does PWM matter for your PC fans?
There are a couple of reasons why you may care, and the first one is quite simple: longevity. It doesn’t matter what it is, if you use a product of any kind at 100% of its maximum output, it’s going to have a much shorter life span than if you use it at 50%. This is no different with PC fans and is probably why most users never want to run their fans at 100%. Well, that and the noise they would output at full speed.
Natural segue – the next reason is noise! While it may be good for a quick laugh, no one wants their PC to sound like a jet engine about to take off on a runway. We want our PCs quiet so that we can enjoy what we are doing with as little distraction as possible.
The third reason is going to be temperature. With PWM fans, you can set custom fan curves in programs like Fan Control, so that if your CPU or GPU hits a certain temperature, the fan’s RPM gets higher until the CPU or GPU drops below the specified temperature again. This simply means that when your PC is doing an intensive task, the fans can kick in automatically to help cool things down. This is designed to stop your computer from overheating. When your temps drop back down, or you stop doing the intensive task, the fans can then revert to a slower RPM, increasing their longevity and reducing their noise output.
It may take some time to get your custom fan settings performing as you’d like, but it is one of those features that will be worth figuring out; and once it is set correctly, you shouldn’t have to worry about it again!