Clock per instruction

Question

What is the difference between Effective CPI and Average CPI  ?

A program is run on 40 MHZ with instruction mix and corresponding clock cycle count.

Determine :   * Effective CPI    * Average CPI     

Instruction	Clock Cycle	Instruction Count
Arithmetic	1	45000
Floating Point	2	32000
Data Transfer	2	15000
Control Transfer	2	8000

 

Answer 1

Execution time = #f instructions/program * Average clock cycle/ instruction.

Average Clock cycle/instruction = [(45000*1+ 32000*2 + 15000*2 + 8000*2)/45000 +32000+15000 +8000]

                                                         =155000/100000 = 1.5cyles.

Cycle Time = 1/frequency , frequency = 1/40MHz = 0.025*micro second.

Effectice CPI = 4*1.5cycles= 6 cycles.

Comments

Difference b/w Effective CPI and Avg CPI ?

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Why u multiplied by 4 here ? Is it total number of instructions ?

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yes