Lecture 3:performanse measure

3.Performance Measures

In this section, we consider the important issue of assessing (تقييم) the performance of a computer by studying three measures:

a) CPI (clock cycles per instruction)
b) MIPS (million instructions-per-second)
c) MFLOPS (Million floating-point instructions per second)

3.1 CPI (clock cycles per instruction)

Performance analysis should help answering questions such as how fast can a program be executed using a given computer? In order to answer such a question ,we need to determine the time taken by a computer to execute a given job.

We define the clock cycle time as the time between two consecutive rising (صاعد) edges of a periodic clock signal :


The time required to execute a job by a computer is often expressed in terms of clock cycles.

We denote the number of CPU clock cycles for executing a job to be the cycle count (CC), the cycle time by CT, and the clock frequency by f = 1/CT. The time taken by the CPU to execute a job can be expressed as :