Things are a little clearer on the PPC601 (not sure about the later models) because the die was mounted in a flip chip configuration, where the die is turned upside down and attached to the package. So on a PPC601, there's a little rectangle in the middle of the full packaged chip. That little rectangle is the silicon die. Everything else is the package which connects conductors to metal bumps on the die and runs them out to the edge of the chip as wires.

If you have an x100 model (or original 7500 CPU card) laying around, you can see this by removing the heat sink and cleaning off the heat sink compound--but be sure to apply fresh compound when you're done gazing.