You can tell if your particular Power Mac G4 computer is PCI-based or AGP-based two different ways:

1) You can check your systems profiler under the Apple menu.

2) You can determine if your particular Power Macintosh G4 computer is PCI-based or AGP-based by external inspection. Look at the sound ports on the back of the computer. On Yikes! PCI-based models, the sound ports are horizontally aligned, and on Sawtooth AGP-based models, the sound ports are vertically aligned.

The AGP-based Power Macintosh G4 systems announced on January 9, 2001 and discontinued on July 18, 2001 use a different logic board design than the earlier Sawtooth models, with four PCI slots (instead of three),Besides the extra PCI slot, the sound ports have been moved to the top, and the "soft" power plug has been removed.