In the following guide we want to give a brief introduction to setting manual fan curves.
PWM vs DC Fan Control
There are two main options for adjusting the fan speed via a computer’s motherboard:
- The fan speed can either be regulated by adjusting the supply voltage (DC, lower voltage = lower speed) or
- by controlling the fan via a PWM signal.
The PWM signal resembles a square wave that regulates fan speed via its duty cycle. The duty cycle is a percentage, where 100% means running at full speed.
Most fans will stop at a duty cycle of 0%, while some are designed to keep running at 0%. If a fan stops at 0% it will be mentioned in the fan specifications on our website:
3-Pin Fan vs 4-Pin Fan
Fans used in computers are usually either 3-pin or 4-pin fans. (There are some exceptions when using pre-built systems from manufacturers such as Acer, Apple, Dell, HP, Lenovo, etc.)
Our Noctua 4-pin fans are easily identified by “PWM” in their product name. The fourth pin allows for PWM speed control via the motherboard, or even another device that is capable of controlling PWM fans.
3-pin fans can only be controlled by adjusting the voltage that they are supplied with. Many motherboards can control fans both ways, by setting the fan mode to “DC/ Voltage” or “PWM”. It is also possible to control 4-pin PWM fans by adjusting the supply voltage. However, when controlled via PWM, the fan speed can be adjusted more precisely, and it can be set to lower values compared to voltage control.
Therefore, for use in a PC, we would strongly recommend using 4-pin PWM fans and controlling them via PWM through the motherboard’s BIOS or UEFI whenever possible.
4-pin PWM | 3-pin | |
Motherboard fan control PWM based |  |  |
Motherboard fan control voltage based |  |  |
Customising Fan Speed
If you want to further optimise your fans’ sound and performance, we recommend setting a manual fan curve in the BIOS after setting up your PC.
The default fan curves can be set too aggressively (i.e. too steep, too high fan speeds at low temperatures) and are, of course, not fine-tuned to a specific fan model.
Example of a default fan curve
While fan speeds can be adjusted by using fan control programs as well, we recommend setting the fan speed via the PC’s BIOS or UEFI to avoid any software issues.
To enter the BIOS or UEFI of your motherboard, press the DEL key on your keyboard as the computer boots up. Sometimes another key (such as F2) needs to be pressed on start-up – this information will be displayed on the start-up screen or is otherwise mentioned in the motherboard’s manual.
Once in the BIOS/ UEFI, navigate to the fan settings. Depending on the motherboard manufacturer and motherboard model, the fan settings can be found in either the hardware monitor, Qfan control, the system tab, Smart Fan Mode, or a similarly named setting. If the fan settings are difficult to find, please refer to your motherboard’s manual to find out how to enter the fan settings.
First, depending on the motherboard model, it may be necessary to run a fan test, often called “Tuning”, before being able to adjust fan speeds. This feature will determine the installed fan’s minimum speed and minimum PWM duty cycle. Running this test makes it possible to utilise the entire range of speed possible with your specific fan model. Other motherboards do not require this test. Information on this will be provided in your motherboard’s manual.
Next, the manual fan curve can be adjusted to fit your needs. The fan curve’s x-axis represents the temperature (typically of the CPU), whereas the y-axis represents the fan speed. The fan curve can be adjusted by dragging the points on the curve to a different position on the graph. Each dot determines the fan speed at a specific temperature. For example, a dot at 40°C and 40% will make the fan run at 40% once the temperature reaches 40°C.
We do not wish to recommend a universal fan curve, as that would defeat the purpose of a manually set curve. However, we will explain two possible fan curve settings for case fans, which can be adjusted for your setup. We recommend a similar fan curve with slightly higher speeds for the fans on CPU coolers. As a rule of thumb 10% can be added to the PWM values for CPU fans.
Example fan curves for case fans
To fine-tune the manual fan speeds for your specific setup, we want to consider three usage-scenarios for setting the points on a fan curve:
- Low load: Normal everyday use which includes office use or browsing the web
- Medium load: A more demanding scenario with increased loads including video games
- High load: Includes CPU-intensive video games and video editing and rendering, making the CPU run at maximum load
1.) A gradual fan curve
[1: 20°C – 20%, 2: 40°C – 40%, 3: 55°C – 605, 4: 70°C – 70%, 5: 90°C – 100%]
Low load: For the first scenario, light PC use, you will want to set the fan curve to a value that is still very pleasant concerning fan-noise, but also keeps the CPU at a comfortable temperature. In the exemplary fan curve, this would be around the 40°C – 40% PWM mark.
Medium load & High load: The more demanding scenarios, including gaming and video editing, has the fans run at around 60% - 70% PWM. And finally, above 90°C we want to have the fans run at 100%, as sound becomes subordinate to keeping the CPU temperatures under control at this point.
Your CPU will also influence how to set the fan curve: The hotter the CPU, the more aggressive the fan curve needs to be.
2.) A fan curve with steep changes
[0: 0°C – 0%, 2: 60°C – 60%, 5: 80°C – 100%]
This fan curve is set in a completely different way: As changes in fan speed can be perceived as more noticeable or distracting than a constant fan speed, this fan curve tries to avoid changes in fan speed as much as possible. However, the rapid increase in fan speed at 60 °C and 75°C will be very noticeable. This setting would, therefore, only be advisable, if your temperature does not frequently change to values that would cause a change in fan speed. If your temperatures stay within 60°C – 75°C during gaming, the fan will not change its speed, if the temperature frequently changes between 50°C and 60°C, however, the rapid speed change at 55°C could become unpleasant. If two points are connected by a constantly increasing line, the fan speed will change even with minuscule changes in temperature. In the example picture above, you will notice for this reason, how most of the fan curve is, in fact, a straight line parallel to the x-axis. We have used a setup with the following values here: (0) 0°C – 30%, (2) 60°C – 60%, (5) 80°C – 100%
Points to consider
How do you set the perfect fan curve for your setup?
That will depend on your main concerns, which in turn will be determined by factors such as personal goals (e.g., “I want the lowest possible CPU temperatures.”), but also factors such as the location of your PC. Is it placed in a living room right next to you? In that case, noise certainly plays a bigger part than if the PC was in an extra room, or if you are only using your PC with headphones on.
Consider what your main goal is when setting your fan curves, and make adjustments accordingly:
- Performance vs Noise
For optimal performance, higher fan speeds are ideal. If your focus is on low noise, however, you can consider setting your fan speeds lower. As a low noise enthusiast, you can even consider running your case fans at 20% until the CPU reaches a temperature of 60°C (as an example).
- Temperatures
While running your CPU at any temperature below the specified maximum values by Intel (TJUNCTION) and AMD (Tjmax) can be considered safe (these temperatures are often around 100°C for most modern CPUs), some users are keen on keeping the CPU temperature as low as possible, even in idle. To achieve that, the fan speeds need to be adjusted to your wishes, so that good airflow is achieved in the computer case, even at low CPU temperatures, i.e. higher fan speeds at lower temperatures.