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Information about our fan curves

Introduction

This article explains how fan curves work in principle and which additional mechanisms operate in the background to optimize fan behavior and prevent sudden ramp-ups under low load.

What is a fan curve?

A fan curve describes the relationship between temperature and fan speed. The higher the temperature, the higher the fan speed.

Example:

xmg-apex-17_m25_fan-curve_cpu.png

Axis labels:

  • Temperature horizontal (°C)
  • Fan speed vertical (%)

However, such curves are only a simplified representation. In practice, we use additional logic to reliably absorb performance peaks without the fans appearing nervous or restless at low or medium loads.

Differences between performance profiles

Performance profiles are deliberately tuned towards different priorities. Typical objectives:

  • Performance/Overboost: maximum responsiveness and thermal headroom.
  • Entertainment/Enthusiast: best compromise between performance and noise level, with maximum efficiency.
  • Quiet/Silent/Balanced: minimum noise level, but with strict power limits.

A reactive profile can counteract load changes more quickly and make better use of boost potential. A quiet or balanced profile deliberately allows more leeway so that short load spikes are not immediately audible.

Temperature averaging to cap off peaks

CPU and GPU temperature sensors provide highly dynamic readings. CPU hotspots in particular can fluctuate significantly within fractions of a second without resulting in sustained load.

To prevent the fans from reacting to every single occasional spike, we use a smoothed temperature value calculated over several seconds instead of the raw real-time reading.

Result:

  • Fans do not spin up at every millisecond temperature peak
  • Less nervous behavior with mixed workloads
  • More stable acoustics during video conferences, web browsing, office work, and short burst loads

Stable speed levels thanks to hysteresis

A fan curve usually consists of steps or thresholds, so there is not a specific fan speed assigned to every single temperature value. Without additional logic, the system would constantly switch between two steps when temperatures hover at or near a threshold.

Hysteresis helps prevent this with the following logic:

  • Temp Up: switch to a higher speed above this temperature
  • Temp Down: switch back only once the temperature falls below a lower threshold

Example:

  • Above 75 °C → fan increases to a level of 80% fan duty.
  • Only when the temperature drops below 70 °C does the fan return to the previous level of 65%.

This bandwidth prevents constant oscillation and ensures that fan speeds appear smoother and more reliable in practice.

The width of this bandwidth varies depending on the profile.

  • Performance: narrower, faster, more responsive
  • Quiet/Entertainment: wider, quieter, more comfort-oriented

Why do fans sometimes spin up briefly in idle mode?

Despite all the mechanisms described above, occasional fan activity in idle mode cannot be avoided completely. The activity is caused by the operating system’s power consumption: if you leave the system completely idle for a few minutes without any mouse or keyboard input, Windows may begin processing pending background tasks. These include:

  • Windows maintenance and indexing
  • Virus scanner or Defender scans
  • Update mechanisms
  • Telemetry, sync services, driver tasks

These processes can generate very high CPU load for a short time without you noticing it directly. Depending on the active performance profile, the fans may respond quite noticeably to this background activity.

When you are actively working - writing, browsing, attending meetings, gaming - this background behavior does not occur. Even during pure video playback, which is technically also a form of idle, Windows will not start background tasks. Windows recognizes when video is playing, both in browsers and in dedicated video players, and temporarily suspends background activities and sleep timers.

So when you sometimes read in tests and reviews that fans supposedly ramp up "for no reason" when idle, we would like to point out that with well-designed fan control, this is less of an issue in practice than it may seem.

What can I do as a user to reduce fan noise?

If the fans are noticeably loud even in Balanced profiles despite apparently low load, it is worth taking a closer look at the possible causes.

Fans do not spin up without reason. In most cases, they respond to unnecessarily high power consumption, for example if the CPU or dedicated GPU is active, or, in devices that have been used for a long time, to a cooling system that is no longer operating optimally due to dust buildup.

We provide two additional FAQ articles on this topic:

This FAQ article explains how to use HWiNFO64 to quickly determine whether unexpectedly high power consumption is occurring in idle, typically because the NVIDIA GPU remains active or background software is unnecessarily occupying the CPU. Once these major consumers are eliminated, both noise level and battery consumption often decrease significantly.

In older devices or systems exposed to intensive use, dust accumulation is the most common reason fans start spinning earlier and faster than necessary. Regular cleaning - at least once a year, or every six months with heavy use - restores airflow and improves both temperatures and noise levels without requiring any changes to fan control.

Following these two guides are the most sensible first steps if fans are perceived as "too loud" in everyday use. Other measures, such as undervolting or further adjustments to fan curves, generally only come later, after any underlying issues have been dealth with.

Further information