
I have 2 knobs on the front of my PC that regulate the speeds of my 4 case fans and another knob to regulate the speed of the 2 fans near the harddrive. This is by the temp display.
But that is different than what you are talking about. If I had all of my fans running on full all the time it would be too loud. Plus the LED's are dimmer when tthe fans are on low which is nice if you don't want alot of blue LED output.