In that guide, PurePower may not be able to handle high clocks.
Hmm... guess I'm out of luck then. I can only clock my quad to 3.80GHz...
But sincerely, IMO, Tier 1 should only be used for suicide runs. Tier 2 for really insane clocks for short sessions... and Tier 3 for 24/7 use at affordable prices. But hey, that's just me.