ok, just got a 2nd ATI 3870 for my mac pro 2008. THe fan is just as loud or slightly louder than the 1st one. *ugh*. So I downloaded smcFanControl 2.2.2 to see if I can up the fan settings to cool the machine down to hopefully slow lower the fans on the 3870's. I cranked them up about 30%. What does IO, Exhaust and PS relate to. I assume the fans to these components What settings are you using and how did you ascertain the percentage increase (or decrease)?