& to make the thread drift a bit, Purple of the big 3, ( Sabs,Zep & Purple were in my view the biggest & most significant progenitors of heavy rock-metal of the 70's), were alone in playing REALLY fast stuff. Fireball & Burn to be exact.
Ever hear the debut of Captain Beyond, which featured intitial Purple frontman Rod Evans from the days when the Purp began life as a psychedellic pop outfit? That's another early example of fast-playing hard rock. Sir Lord Baltimore from the same era also have a couple of tracks in the same vein.