It would be good to provide more details...
I'm assuming you have some kind of software loop that you wrote - can we see it? Any other applicable code we can look at?
Where are you measuring the clock?
How are you measuring the clock - are you using a scope or something else?
Thanks for your response but please ignore my post. Something was wrong with my initial test ... and the results were spurious
clock() does tick in microseconds. - sorry