Question: Intel’s Sandy Bridge launch just brought its desktop CPU line up to 3.8GHz, but I remember that the Pentium 4 got up to 3.8GHz before being cancelled. So why is it that Sandy Bridge is just now getting to the clock speed levels that the Pentium 4 was at years ago? And how is it that Sandy Bridge still manages to outperform the older Pentium 4, even though it has a lower clock speed?

via Ask Ars: what’s the relationship between CPU clockspeed and performance?.

Worth a read.