What is Semi-Fanless? Improving Silent Performance Under Low Load

The “semi-fanless” feature is attracting attention from users who want a quiet PC environment.

This is a function that automatically stops the fan when the computer load is low, reducing noise during low loads and improving quietness.

It is often installed in graphics cards and power supply units, but there are some precautions to be aware of, so this article will explain those points as well.

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What is Semi-Fanless?

This section explains the basic knowledge of semi-fanless and which PC parts may have this feature.

Function to Stop the Fan During Low Loads

Semi-fanless is a function that automatically stops the fan when the computer load is low, reducing noise during low loads and improving quietness.

PC parts inside a computer generate heat, so fans are always spinning to cool them down.

However, if the fan keeps spinning even when the workload is light or the temperature is low, the noise can be bothersome, and the fan is spinning unnecessarily when cooling is not needed.

With the semi-fanless function, the fan can be stopped to keep things quiet when the computer is not generating much heat, and it will automatically start spinning to cool down when the temperature rises.

Thanks to this, it is popular among users who prioritize quietness because it balances “quietness” and “cooling”.

Graphics Card

Some graphics card fans are equipped with a semi-fanless function.

For graphics cards, semi-fanless means that the cooling fan automatically stops during idle (when the GPU is not under load) or during light tasks, making the system completely silent.

Basically, graphics cards only experience high loads during games, 3DCG, 3D modeling, or other demanding graphics processing. In these cases, the fan needs to spin for cooling.

However, light tasks like internet browsing, office work, or video playback do not put enough load to require the fan to spin, so having a fanless function allows the fan to stop completely, improving quietness during low loads.

However, the conditions and temperature thresholds for this function to activate differ by product.

Also, some products allow users to customize the threshold using the manufacturer’s software, so users who value this function should check carefully.

There are big benefits for users who prioritize quietness, but if the computer is used in a way that keeps it hot for long periods or if the airflow inside the PC case is insufficient, there is a risk that the fan will start up late and the temperature will temporarily rise, so caution is needed.

The semi-fanless function has different names depending on the manufacturer.

• ASUS: 0dB Technology
• MSI: Zero Frozr
• Gigabyte: 3D Active Fan

Each manufacturer uses its own name, so use this as a reference when checking specifications.

For most recent graphics cards, about 70-80% support the fanless function, so it is not a rare feature.

Especially, many graphics cards from the RTX 30 to 40 series and later come standard with this feature, making it a common specification.

Also, on the Custom PC Tool, graphics cards can be searched by whether they have a semi-fanless function, so please make use of it.

Power Supply Unit

The semi-fanless function in power supply units allows the cooling fan to automatically stop when the power load or internal temperature is below a certain standard.

This means that during idle or light tasks, the fan stops completely, improving quietness.

When a certain temperature (for example, about 40–50°C) or output load (for example, over 30%) is exceeded, the fan automatically starts spinning to cool down.

With this kind of control, it balances quietness and efficient cooling, making it suitable for users who want a quiet environment.

However, the operating conditions for the semi-fanless function differ by product. Some products allow the function to be turned ON/OFF with a physical switch, while others are fixed from the factory.

Also, while there is high quietness during light use, for tasks that always put a high load on the system, the fan will run frequently, so the benefit of semi-fanless may be limited.

About half of recent power supply units support this semi-fanless function, and it is often found in models with high power capacity, such as 800W.

Also, on the Custom PC Tool, power supply units can be searched by whether they have a semi-fanless function, so please make use of it.

PC Case Fan [With Conditions/Limitations]

The semi-fanless function for PC case fans is mainly controlled by the motherboard or a fan controller, stopping the fan below a certain temperature and starting it automatically when the temperature rises.

However, running PC case fans in a semi-fanless way is not generally recommended from the perspective of airflow inside the computer, so it is not common.

PC case fans themselves usually do not have built-in sensors or control circuits, but 4-pin fans that support PWM control and motherboards or software that can control semi-fanless operation make it possible to run them semi-fanless.

However, not all motherboards support completely stopping the fan, and sometimes the minimum fan speed cannot be set to zero.

Also, fans themselves have minimum speed specifications, so even if they support PWM control, some products cannot physically stop.

After checking several products, many can only be lowered to about 400rpm at minimum, so the hurdle for introduction is higher compared to other PC parts.

Even if it looks like it can be set to 0%, if the fan itself does not support 0rpm, it will not actually stop and will keep running at the minimum speed (e.g., 400rpm).

In other words, semi-fanless operation is only possible if both the motherboard’s control function and the fan’s specifications support it.

Here are the reasons why semi-fanless operation for PC case fans is not recommended:

• Weaker overall case heat exhaust
  Heat sources like memory, GPU, and M.2 SSDs have a harder time dissipating heat, making internal temperatures rise more easily.
• Heat can build up more easily in summer or under high loads
  In high ambient temperatures, there is a risk that internal temperatures will rise rapidly while the fan is stopped.
• Risk of shortening lifespan due to insufficient cooling when the fan is stopped
  Heat from hot components can build up, potentially causing faster deterioration over the long term.
• Limited improvement in quietness even if the fan is stopped
  The noise from the CPU cooler or GPU fan is usually louder, so stopping the case fan does not make much difference in perceived noise.
• Setting up semi-fanless control is troublesome
  The conditions are strict, and adjusting the fan curve requires experience and time.
• Most motherboards are not designed for this operation
  Manufacturers usually design fan control for constant low-speed rotation, so complete stopping is an exception.
• Designs that prioritize cooling over quietness are more stable
  Always ensuring airflow makes it easier to respond to temperature changes and is safer.

As shown above, while semi-fanless can improve quietness, it is not very suitable for general configurations when considering cooling and stability.

If you want to run PC case fans semi-fanless, it is better to consider it only for advanced users who are used to building custom PCs.

Also, even if you prioritize quietness, the noise from the CPU cooler or GPU fan is usually louder, so stopping the PC case fan not only increases risk but also does not improve quietness much, making semi-fanless case fans uncommon.

Benefits of Semi-Fanless

This section explains the benefits of semi-fanless.

Improved Quietness During Low Loads

The biggest feature of the semi-fanless function is that it stops the cooling fan when the computer is under low load, reducing operating noise.

This is a big benefit for users who prioritize quietness.

Usually, many cooling fans are designed to spin constantly regardless of system temperature, so even during light tasks, the fan keeps spinning and making noise.

Especially at night or in quiet work environments, even a little fan noise can be bothersome for some users.

With parts equipped with a semi-fanless function, the fan automatically stops during light tasks such as web browsing, watching videos, or business tasks like document creation.

This completely eliminates fan noise, so it is recommended for those who want to work in a quiet environment.

Slight Power Saving Effect?

Semi-fanless stops the fan during low loads, reducing power consumption and providing some power-saving effect.

However, the power consumption of fans is very small, and as a percentage of the total computer power consumption, it is really minor, so it is not something to worry about.

Also, it is said that fans consume the most power when starting up, so if the fan repeatedly starts and stops, the number of startups increases.

When a fan starts spinning, an inrush current is generated to move the motor, which is a large initial load because it starts from a stationary state.

This inrush current causes the fan to consume more power at startup than during normal operation.

Therefore, it is hard to say that it always leads to power savings, and even if there is a power-saving effect, the fan’s power consumption is so small compared to the whole computer that it cannot be considered a big benefit. In fact, in some cases, power consumption may even increase.

Disadvantages of Semi-Fanless

This section explains the disadvantages of semi-fanless.

Not Suitable for High-Load Environments

Semi-fanless is designed to stop the fan during low loads to improve quietness, but its benefits may not be felt much during high-load tasks.

For example, in high-demand tasks like 3D gaming, image/video editing, or AI processing, the opportunity to reach the “below a certain temperature” condition for stopping the fan is much less than during light everyday use.

As a result, the fan may always be running or only stop occasionally, so the benefit of quietness may not be noticeable.

In other words, for high-load tasks, even if the semi-fanless function is installed, it may be “almost the same as the fan always spinning.”

Therefore, for these uses, it is better to prioritize overall cooling performance and airflow efficiency rather than whether the semi-fanless function is present.

Temporary Weakening of Heat Exhaust

Semi-fanless does not start the fan until a certain temperature threshold is reached, so the fan may start up a little late, and the internal temperature of the computer may rise rapidly during that time.

This is especially likely to affect performance during tasks with a sudden increase in load, as the cooling response is slightly delayed.

For example, high-load tasks like 3D gaming or image/video editing.

Also, some semi-fanless products are designed to prioritize quietness so much that even when the fan is running, the speed is kept low, and if high temperatures last for a long time, cooling may not keep up, possibly causing thermal throttling.

For these reasons, in work environments that always require high performance or in hot environments without air conditioning, it is better to use a cooling design with fans that always spin rather than semi-fanless.

Especially for workstations or systems intended for long continuous operation, there are many situations where cooling performance and responsiveness should be prioritized over quietness.

Frequently Asked Questions About Semi-Fanless

This section explains common questions about the semi-fanless function.

Does Fan Lifespan Get Longer or Shorter?

Many people wonder how the lifespan of a semi-fanless fan compares to a regular fan that always spins.

However, to conclude, it cannot be said for sure whether the lifespan is “longer” or “shorter,” but in most cases, it will last longer than the lifespan of the computer itself (about 3–10 years), so it is not something to worry about.

First, the opinion that lifespan is shorter is based on the idea that frequent starting and stopping puts stress on the fan.

With semi-fanless, the fan may start and stop many times, and the moment the fan starts spinning is said to be when the most stress is placed on it.

At this time, the motor and bearings are under the most load, so frequent starting and stopping could result in a shorter lifespan.

On the other hand, the opinion that lifespan is longer is based on the idea that the fan’s total running time is shorter.

Compared to a fan that always spins, the motor’s total running time is shorter, so mechanical wear is reduced, and the lifespan may be extended.

Since the fan runs less, the load on the bearings and shaft is also smaller, so stable operation for a long time can be expected.

There are both opinions, but there is no accurate data on how lifespan changes with repeated starting and stopping, so it is honestly unclear whether the lifespan is longer or shorter.

However, in my experience, the computer itself (about 3–10 years) usually reaches the end of its life before a semi-fanless fan fails, so I don’t think you need to worry much about semi-fanless shortening the lifespan.

Summary: Users Who Prioritize Quietness Should Consider Semi-Fanless!

This article explained semi-fanless for custom PCs, including compatible PC parts, benefits, and disadvantages.

Here is a summary of the key points.

Semi-fanless is a function that improves PC quietness by stopping the fan during low loads.

Especially for users who mainly do everyday tasks or light use, it has the benefit of making the work environment more comfortable.

Many graphics cards and power supply units are equipped with the semi-fanless function, so there are plenty of parts to choose from.

Also, running PC case fans semi-fanless has many restrictions and limited quietness benefits, so it is not recommended for beginners.

It is important to choose parts according to your own usage style, whether you prioritize quietness or cooling performance.

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