7455 and 7457 are "G4" CPU's
What you associtate with "G5" processors are not a continuation of the PPC range.... they're a new architecture called eBook.... the first of the "G5's" will be the e500, it is NOT code compatible with the current PPC CPU's.
That's the dissemination. Mull over it how you will.
Neil Thomas, AKA MiniBobF