My southbridge fan has today suddenly decided to get pretty loud. When the computer the boots the fan spins up to its normal rpm and is nearly silent, then seems to step up to a faster rpm and is pretty loud. In nvidia control panel its always been set to spin at 100%. Just to see what was up I decided to set it down to 80%. It immediately stopped spinning and you can see and hear the motor trying to turn the fan over but it cannot. Could it be defective? Or maybe a voltage problem?