i m using speed fan to reduce my cpu fan speed
phenom X 2 965
msi 790gx g65
amd stock cooler
fan runs at 6000rpm which is loud so using speed fan i reduce speed and noise
is reducing speed safe or can it damage
Reducing the speed is likely to extend the motors life, speed fan slows down the fan in the same way your motherboard does so its perfectly safe.
Still go into bios and check its settings so that you dont have to rely on speed fan, i have mine set on optimal so that it sits at about 3300RPM normally but if im playing a game for a while when i come out its at 5500-6000RPM to keep it cool.