Fan Profiles and Curves

Fan Profiles and Curves

A fan curve is a graph that maps temperature to fan speed. At low temperatures, the fan runs slowly or stops entirely to keep noise down. As temperature rises, the fan speed increases to provide more cooling. Setting the right fan curve is the key to a quiet system that stays cool under load. Most motherboards let you configure fan curves in the BIOS or through software.

The default fan curve in most BIOS settings is designed for compatibility, not silence. It often ramps up the fans too aggressively, causing unnecessary noise. A good custom curve keeps fans at a low, inaudible speed up to about 50 degrees Celsius, then gradually increases to 100 percent speed at around 80 degrees. This gives you silence at idle and full cooling when you need it.

Different fans have different response characteristics. Case fans should generally follow the system temperature, which is the temperature inside the case. CPU fans should follow the CPU temperature. GPU fans are usually controlled by the graphics card itself. Some motherboards let you assign different temperature sources to different fan headers, which gives you fine-grained control.

Fan hysteresis is an important setting that prevents rapid speed changes. Without hysteresis, a fan might spin up when the CPU hits 60 degrees, then spin down when it drops to 59, then spin up again when it hits 60, creating an annoying cycling noise. Hysteresis adds a delay, so the fan only changes speed when the temperature changes by a certain amount, like 5 degrees.

Software like FanControl gives you even more control than the BIOS. It can combine multiple temperature sensors, create custom fan curves with complex logic, and even control fans based on GPU temperature or hard drive temperature. For most users, a simple BIOS fan curve with a flat low-speed section up to 50 degrees and a gentle ramp to 100 percent at 80 degrees is all you need.