PWM fans?

[ddan49]

Hello,

So I've been looking at some case fans (silent), and found some cougars. After I got away, I found these case fans:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835553002
http://www.newegg.com/Product/Product.aspx?Item=N82E16835553001

The first one is PWM, the second one isn't. I'm not sure what Pulse Width Modulation does... and is my motherboard compatible?

Extreme3 Gen3

I went to Wikipedia, but I don't see how changing voltages is unique to PWM fans.

Thanks!

 

[MegaMan1]

PWM does not change the voltage. It turn it on to 12v for the pulse width and then off.
There is no reistor switched in series with the fan to slow it down. It is just turned on for a pulse and then off , etc. Think fast like digital. the wider the pulse to faster the fan.

 

[ddan49]

So why would I get it?

 

[MegaMan1]

It's green baby. Resistors waste energy plus the computer can not control them. It can contol pwm and set the fan to what is needed. Speed up when hot. The pulse could be 99% wide so the fan would be the same as at 12V, or when not needed much slower and quiet.

 

[ddan49]

So it changes speed based on the temperature? Without you changing it yourself? If so... that's awesome. It'll be like laptop-style cooling!

 

[DJDeCiBeL]

So it changes speed based on the temperature? Without you changing it yourself? If so... that's awesome. It'll be like laptop-style cooling!

Yep, and it can either be the automatic settings (usually more than one) that the motherboard provides or you can set a manual fan curve that suits your needs, if you want. Same idea, though.

 

[ddan49]

Whoa. I know what I'm getting for my case fan. Although I guess it would be better to have it positioned in a side panel over the graphics card... as an intake, is it realistic? I'll be using the Fractal R3, so I wanted a second fan to put in as intake in the front panel (it only comes with one). To take advantage of the PWM, though, it should be positioned over something that emits heat... like a CPU or a GPU. Maybe as an exhaust?

 

[DJDeCiBeL]

Well, since they will be plugged into the case fan headers, they won't be tied to the CPU or GPU temp, just the ambient temp in the case (what you may know as motherboard temp), and that is usually always much cooler than either the CPU and GPU, especially when they're not idle, so keep that in mind. That basically just means that you'll want to set the speeds accordingly for lower temps than you would for a CPU fan (because obviously, the ambient temp will never get as hot as the CPU or GPU die temps).

 

[MegaMan1]

The fan is not sensing the heat. The motherboard or other device senses temp and makes decisions on what to do. The contol device changes the pulse width and the fan responds. Fan in cpu plug responds to cpu temp etc.

 

[ddan49]

Ah. So overall, do you think it's worth the extra $5? I mean, more functionality for a cheap price is always good, but is PWM necessary? For an overclocker?