I noticed when browsing some folks' hints for reducing fan noise in the Power Mac G5, that many folks seemed alarmed that their CPU temps would go up unless they had the fans churning by manipulating Energy Saver prefs. CHUD Tools (linked on this page
) allows you to turn off processor "napping," which eliminates the relay noise caused by the disconnection of processors in preparation for nap mode.
Don't worry about the heat from specific areas. Just because the temps jump from a very low 9 or 10 degrees Celsius to upwards of 80 degrees does not mean that you are sacrificing your processor or its lifespan. Sure, you may notice a slightly reduced lifespan in processors that worked harder or were cooled more sparingly, but by the time they wore out, the machine would be obsolete and gathering dust somewhere.
The zoned cooling of the Power Mac G5 is brilliant. However, it leads people to believe that a particular zone is too hot. The heat generated by processors that are properly heatsinked and ventilated is normal and within the range the processors are designed to run in.
For me, I had to disable the manual setting of "Highest" in Processor Performance in Energy Saver and put it to "Automatic" to achieve some quiet. For some reason, the fans are not intelligently cooling in my machine when this setting is engaged. They vary in speed, but still are noisy even when nothing is on and the unit is in Sleep. Automatic seems to bring the fans down and kicks them in as needed. So if you think your fans are a bit too noisy, try Automatic mode.