Replaced the Hard Drive with an SSD in my 2010 High Sierra iMac and got the steadily mounting fan noise following start up. Wasn't expecting that until I looked it up and found it to be a common occurrence following 3rd party HD upgrade. Downloaded this software; automatic setting made no difference but pressed SMART option and lo! fans instantly quietened and I now have a speedy and near silent machine. So impressed, I donated.
Have no idea how this thing works! All I see is RPM, I tried to reduce the rpm but fan is still running at full speed! The Auto/Manual buttons have no effect whatsoever!