on the clock

go overboard
to do or say something that is too extreme for a particular situation
I hope politicians will not go overboard in trying to control the press.
With the new price cuts coming, I might be tempted to build a Q9650 or Q9550 to tided me over the next 3 yrs and then go with an upgrade.

on the clock
　a car with 43,000 miles on the clock

for Phenom 2 to be able to compete with a Q9400/Q9550 or above it has to be able to hit 4.2 Ghz on air atleast, because the Q9400/Q9550 are faster clock for clock and can hit 3.8/4.0Ghz respectively. That is the problem.
opening salvo
the first in a series of questions, statements etc that you use to try to win an argument