The G series (started with G3, I don't know why) was all PPC.
The 'G' prefix refers to the generation of
PowerPC CPU used. The appearance of the G-word in Apple marketing effectively started with the G3 models. The preceding 601, 603 and 604 CPUs were pretty much used in parallel until the G3 appeared. Here follows the historical sequence, with the year of their introduction in Macs in parentheses:
G1: PPC 601 (1994)
G2: PPC 603, 604 (1995)
G3: PPC 750 (1997)
G4: PPC 7447, 7450, 7455 (1999)
G5: PPC 970fx (2003)
