Os hago un copypasta de otra web.
Hysteresis is generally not useful with such steep control curves. I picked an excessive 10C as a quick, easy to illustrate example.
Not exactly; GPU does not stay warm because fan is slowed early...
Hysteresis keeps the fan at a higher fan speed more often than not. Less fan earlier means higher temp, with higher temp and hysteresis, fan will be forced back to higher speed. So for steep curves, fan would be rarely go below the max speed you set.
For example, temperature falls (red arrow) and fan slows, then temperature rises, so set fan to the rising or higher fan speed. Or fan resets to 100% until temperature drops past green line.
Otra web:
Basically the last temperature to cause a fan speed change is remembered, and no further changes to fan speed is allowed until the temperature rises/falls past the value you set in that option.
Basicamente la ultima temperatura que causa un cambio de la velocidad del ventilador es memorizada, y no permite cambiar la velocidad del ventilador hasta que la temperatura llegue/caiga sobre el valor que has introducido en esa opcion.
Joder, aún en castellano me cuesta entenderlo.