What is a fan curve?
A fan curve is a simple rule: at this temperature, spin at this speed. It is drawn as a line with temperature along the bottom and fan speed up the side, usually with four or five points you can move. Out of the box most motherboards use a standard curve that is safe but often louder than it needs to be at idle. Setting your own takes a few minutes and is the cheapest way to make a PC quieter.
Where do you set it?
You can set it in the BIOS or in a program in Windows. Every motherboard has a fan control page in its BIOS. The name differs by maker, for example Q-Fan Control on ASUS boards or Smart Fan on Gigabyte boards. A curve set in the BIOS works from the moment the PC starts and needs no program. A Windows program is easier to adjust while you watch temperatures, and it can react to the graphics card temperature, which the BIOS usually cannot see. The fans on the graphics card itself follow the card's own curve, and you change that with software, not in the BIOS. The free Configurator app for Windows sets fixed speeds and temperature curves for the fans it can reach.
What shape should the curve have?
Flat and low at the start, a steady climb in the middle, full speed before the limit. The exact numbers depend on your processor, cooler and case, so treat the points below as a starting shape and adjust after testing.
- Idle and light work: keep the fan at one low, constant speed that you cannot hear.
- Do not start the climb too early. Processors jump up in temperature for a second when you open a program, and a curve that reacts to that makes the fans rev up and down.
- Middle of the range: raise the speed gradually, without a steep step.
- Reach full speed several degrees before the highest temperature the part allows, not at it.
How do you stop the fans from revving up and down?
Three settings help. First, keep the low part of the curve flat, so small temperature changes do not move the speed at all. Second, use the delay setting if your BIOS or program has one. It is often called step up and step down time or hysteresis, and it makes the fan wait a few seconds before it follows the temperature. Third, find the lowest speed at which each fan still spins reliably and do not go below it, because a fan that keeps stopping and starting is more annoying than one that runs slowly. Also check the fan mode: a fan with a four-pin plug is controlled in PWM mode and a fan with a three-pin plug in DC mode, and in the wrong mode it may run at full speed all the time.
What about case fans and a liquid cooler?
Case fans move heat out of the whole case, and in a gaming PC most of that heat comes from the graphics card. If your fan program can use the graphics card temperature, let the case fans follow it. If you set the curve in the BIOS, they will follow the processor or a motherboard sensor, and a gentle curve works best there. With a liquid cooler, the fans on the radiator get a curve like any processor fan. The pump is different: it is normally run at a constant speed, as the cooler's manual describes, and should never be slowed down to make the PC quieter.
How do you check that the curve is safe?
Put the PC under heavy load for ten to fifteen minutes and watch the temperatures. A long game session or a stress test both work. The temperatures should rise, level off and stay below the limit the maker gives for the processor and the graphics card. If they keep climbing, the curve is too gentle at the top, or the case does not get enough fresh air. Then listen at idle and lower the first points if you can still hear the fans.
What if a curve is set too low by mistake?
The parts protect themselves. A processor or graphics card that gets too hot slows itself down, and the PC switches off before damage is done, but neither is pleasant in the middle of a game. So test every new curve under load before you rely on it. The Configurator app adds its own guard: if the processor reaches 95 C or the graphics card reaches 88 C, it stops controlling the fans and hands them back to the motherboard and the card. Its build check loads the PC with temperature cut-offs, which is a quick way to test a new curve.