Kindof true. I'd forgotten how much of a Mhz bump the P6 was -- It came out 12 months after the first intel Mac Pro (and ran at 4.7Ghz at the high end).

The P5 was a contemporary of the G5 (although the G5 was really a P4). But it wasn't quite the beast the P6 was.

And the G5 (the PPC 970 in IBM's nomenclature) was an "ultra-light" POWER4 — the POWER5 was ~30% quicker than the G5. POWER never really fell behind at the high end — there was just no real focus on anything except the high-end.