White paper: Highest MHz Does Not Mean Highest Peformance

In fact, processors with high clock rates consume much more power because power dissipation rises faster than operating frequency. All major PC CPU vendors now offer multicore processors that run at lower clock frequencies than older generation single-core processors.

The same argument holds true for embedded processors, which is even more important for embedded products that operate under very tight power/energy budgets such as portable devices-because extending battery life is an important feature that improves product marketability-but it is also true for non-portable devices because consumers do not want noisy cooling fans in their set-top boxs or flt-panel televisions while IT managers want routers and switches that reduce electrical costs by minimizing energy consumption in the data centers. For these reasons, SOC development teams need to achieve performance goals while keeping a lid on clock rates.