After reading the latest PSU article here at SPCR I followed the link to formfactors.org and found this:
The 4-Wire Pulse Width Modulation (PWM) Controlled Fans v1.3 defines the intended operation of a fan that implements the Pulse Width Modulation (PWM) control signal on the 4-wire fan interface. The introduction of 4 wire PWM controlled fans is a means to reduce the overall system acoustics. The expectation is a 4 wire PWM controlled fan when properly implemented will be significantly quieter than a similar 3 wire fan.
So does this mean quieter fans are coming? Or is this old stuff?
http://www.formfactors.org/developer%5C ... M_Spec.pdf
The 4-Wire PWM Controlled Fans better then 3-Wire?
Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee
I think that the claim is based on the fact that they require all 4-pin fans to have a control range from 30% to 100% in terms of speed (pg. 14). The fan can go even lower (if driven, and fan allows it - see the following pages), and is even allowed to stop. Note that the ability to stop the fan with the PWM signal is not mandatory.
So, to get the most silent operation, motherboard manufacturers just need to set 30% speed with the PWM signal. In our current 3-pin situation, setting PWM to 30% could mean that some fans (our silent fans) won't spin at all. The manufacturer thus has to select a more safe value for the lowest speed.
I think this is the basis for the claim for quieter operation.
Cheers,
Jan
So, to get the most silent operation, motherboard manufacturers just need to set 30% speed with the PWM signal. In our current 3-pin situation, setting PWM to 30% could mean that some fans (our silent fans) won't spin at all. The manufacturer thus has to select a more safe value for the lowest speed.
I think this is the basis for the claim for quieter operation.
Cheers,
Jan
Another (main?) reason for the claimed noise reduction is that these 4-wire fans are designed to work at a high PWM frequency, >20kHz, above our audible range. ( "Normal" PWM is around 30-120Hz, giving clicks & growls)
So if the dog runs out of the room, you'll know your new 4-wire fan is not one of the better models.
http://www.analog.com/library/analogDia ... speed.html
The fans won't be quieter per se, you should hear less noise difference comparing HF-PWM-control and linear control than when comparing LF-PWM and linear, for same-flow settings.
So if the dog runs out of the room, you'll know your new 4-wire fan is not one of the better models.
http://www.analog.com/library/analogDia ... speed.html
The fans won't be quieter per se, you should hear less noise difference comparing HF-PWM-control and linear control than when comparing LF-PWM and linear, for same-flow settings.