If you are not overclocking the CPU, it is better to shut off the fans (or half of the fans ) . For most of the time, we are using less than half of the capacity of the PCU. The new Intel CPU can automatically lower the speed depending on your applications, hence reduce the heat. Unless you receive overheat warnings (most of the mainboard has this function), it is no point to turn on all the fans. Fan noise is annoying especially when you are in quiet environment.
