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performance equation

Run time = number of instructions × average cycles per instruction ÷ clock rate.

The processor performance equation states CPU time = instruction count × CPI × cycle time = instruction count × CPI ÷ clock rate, separating the program and compiler (instruction count), the microarchitecture (CPI) and the circuit and power budget (clock rate).

Examples

  • 2 × 10⁹ instructions at a CPI of 1.5 on a 3 GHz clock take 2 × 10⁹ × 1.5 / (3 × 10⁹) = 1 s.

See also

clock rate cycles per instruction microarchitecture
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