Q: “My G5 looks so cool without the access door – can I just leave it off during the day and replace it at night so that dust doesn’t get inside?”
A: Your Power Mac G5 was designed to be used with the outer access panel (door) in place at all times. In addition to the dust issue you’ve noted, the outer and inner doors work together to direct airflow to cool the components inside the computer, as well as block electromagnetic interference, as required by the FCC. Using the computer with the door open changes the airflow, which can prevent the computer from performing as expected.
It’s no secret that computers generate heat. So, Apple divided the inside of your Power Mac G5 into four discrete thermal zones, compartmentalizing the primary heat-producing components – processor, PCI, storage and power supply. This allows the system to decrease the temperature of a single zone without affecting the others.
Each of the four thermal zones is equipped with its own dedicated, low-speed fans (seven of the nine fans spin at very low speeds for minimum acoustic output). Also, using 21 different sensors, Mac OS X constantly monitors component temperatures in each zone, dynamically adjusting individual fan speeds to the appropriate levels for the quietest possible operation. As a result, the Power Mac G5 normally runs much quieter than the previous Power Mac G4 enclosure.