I wouldn’t get too hung-up over just the processor’s clock speed. Lots of things can influence a processor’s overall performance: bus width (8/16/32 bits), Onboard Cache, Hardware Floating Point acceleration, RAM speed, Graphics processors, and intelligent communications processors can contribute greatly to offloading work the central processor needs to perform to get the job done.
Poorly designed/implemented code and incomplete knowledge of the underlying system hardware can also contribute greatly to pissing-away a significant number of processor cycles.