Back in the day, people often compared computer processors by comparing their clock speed. Now, though, that value means very little when comparing two processors of different families. Ars Technica explains why.
Many of you hardware geeks out there probably know all about this already, but for those of you that maybe don't keep up with the goings-on of the hardware world but are looking to buy a new computer, Ars explains why just looking at a CPU's clock speed - say, 3.0GHz or 3.8GHz - isn't enough to compare two different processors or computers together:
In a nutshell, the Pentium 4 took many more clock cycles to do the same amount of work as the original Pentium, so its clockspeed was much higher for the equivalent amount of work. This is one core reason why there's little point in comparing clockspeeds across different processor architectures and families-the amount of work done per clock cycle is different for each architecture, so the relationship between clockspeed and performance (measured in instructions per second) is different.
Now, the clockspeed-to-performance ratio is stable within the same family of processors, so a 3.4GHz Core i5 CPU will outperform a 3.1GHz Core i5 CPU, all else being equal.
In addition to this, there are a lot of other possible bottlenecks in your computer's system, so it's not as simple as saying "this processor is 3.4 Ghz, so it must be 'faster' than this 3.1 GHz model" (unless they are otherwise equal). Hit the link for more information on why this is and how to effectively compare the performance of two different processors.