[rescue] PC Hardware

[Joshua Boyd]

On Tue, Mar 11, 2008 at 05:42:55AM -0500, Lionel Peterson wrote:

> Then I had a thought - I strapped the case fans (front and back) to the 12V 
> power bus directly (the case came with adapters to do this already) and the 
> noise was gone. Sun of a gun - the issue appears to be the fan control
> of the MB and the fans aren't playing nicely together (probably
> pulsing the power to the fans to throttle the speed). I've never seen
> anything like that before - I'd prefer to have the fans controlled by
> the MB, but I'm happy to have a quiet (and plenty cold) system now...

I have heard of motherboards using PWM (which would pulse the power).
In theory you should hear it though.  The benefit of PWM is that any
time the fan is powered, it is powered at full power, which is more
efficient.