One user submits the following:
"Apple released version 4.1.0 of their CHUD tools. CHUD is used by developer for optimizing applications. One of the components is a system preference panel called "Processor". It enables you to turn off the "Nap" function of the processors, but more importantly it allows you to turn off the second processor of a dual-processor machine.
With version 4.1.0, the interface of the "Processor" panel changed significantly. You can compare the last version (4.0.2) with the current version here.
The significance is pretty obvious. Instead of a static single/dual processor option, there is now room to view 4 processors at once, and to select how many are to be active. Maybe Apple will never actually release a quad-processor G5, but it certainly looks like there is one in development."