Undervolting fans... how is it done?

pedro · Post by **pedro** » Thu Nov 03, 2005 12:24 pm

Yo,

I often read that people undervolt their fans to 5 or 7V. How is this done? Through BIOS? Software? Hardware? I can't seem to work it out.

I have a DFI Ultra-D with a 3200+ in it.

Cheers.

slipknottin · Post by **slipknottin** » Thu Nov 03, 2005 12:40 pm

Your powersupply puts out both 5v and 12v. If you plug your fan into the red(5v) and into a black (negative), then your fan is running at 5 volts. To get 7 volts, you plug the fan into both the red and the yellow(12v). That will give you 7 volts. But it puts a weird stress on powersupplies, so I tend not to do that.

Other than those basics, you can get a whole slew of different things to vary voltages. MB fan headers can often be controlled either by bios or by a program running. There are things like the zalman fanmates that can lower voltages.

silence · Post by **silence** » Thu Nov 03, 2005 2:16 pm

Hello,

Read this.

Read this.

Read this.

According to a review on the web, your motherboard is capable of controlling the CPU, chipset, and "system" fan headers. If you download Speedfan you should be able to program your fans to run according to system/component temperatures. See that website or search the forums for simple questions, and post if you absolutely cannot get it working.

Please don't forget about the technical articles, which the site admin has gone to great efforts to create and maintain. They will answer most of your questions before you'll need to post in the forums.

-DG-

fraz · Post by **fraz** » Thu Nov 03, 2005 3:44 pm

Here's what I did using a Zener diode and a switch:

http://forums.silentpcreview.com/viewtopic.php?t=14753

I don't know why more people don't do it. It's a defined/known voltage drop. But if you have a high current fan, finding a suitable Zener may be harder.