After updating to 10.4.3 I too suffered from excessive fan noise.
Here's how I fixed it (I did a little research on this board and at
www.macosxhits.com).
1.
Open the Energy Saver System Preferences panel, and click the Options tab. Click the Processor Performance pop-up menu, and set it to either Highest or Lowest -- anything other than Automatic. Close the panel, and you're done. Not wanting to give up any performance, I set mine to Highest.
2.
This will keep your G5 even quieter. It will also eliminate any annoying beeps or chirps that can he heard from within during certain processes.
The solution to the chirping problem is to disable "CPU napping." From my understanding of it, this is a lower-power mode for the CPUs, invoked automatically by the G5's power management functions. The G5 wasn't designed to be a 'power conservator' so you may ask yourself what the pint in such functions is. You need to install CHUD, which is short for Computer Hardware Understanding Tools. If not already installed, you can get it straight from Apple, here:
ftp://ftp.apple.com/developer/Tool_Chest/Testing_-_Debugging/Performance_tools/. Download the most recent version (which is 4.2.3 I believe). After installation, look in the Other section of System Preferences, and you'll see a new Processor panel (I think it's called Hardware in 10.3). Open that, and uncheck Allow Nap.
Also note that if you restart, the nap setting is reset, so you'll need to re-open the prefs panel to fix it again. Alternatively,
this older hint explained how to use a simple AppleScript to enable the nap setting at each restart. Change the =1 to =0 in the script, and you should have a "nap disabling" startup item (though I haven't tested this).
Hope this helps!
