Why the clock frequency of embedded system should be as low as possible?

Many developers select an oscillator / resonator frequency that is at or near the maximum value supported by a particular device.

This can be a mistake:

• Many application do not require the levels of performance that a modern 8051 device can provide.

• The electromagnetic interference (EMI) generated by a circuit increases with clock frequency.

• In most modern (CMOS-based) 8051s, there is an almost linear relationship between the oscillator frequency and the power-supply current. As a result, by using the lowest frequency necessary it is possible to reduce the power requirement: this can be useful in many applications.

• When accessing low-speed peripherals (such as slow memory, or LCD displays), programming and hardware design can be greatly simplified - and the cost of peripheral components, such as memory latches, can be reduced - if the chip is operating more slowly

In general, you should operate at the lowest possible oscillator frequency compatible with the performance needs of your application.