Multiple choice

A 5 stage pipelined CPU has the following sequence of stages IF-Instruction fetch from instruction memory. RD-Instruction decode and register read, EX- Execute: ALU operation for data and address computation, MA-Data memory access-for write access the register read at RD stage it used, WB-register write back. Consider the following sequence of instruction:

I1: LR0, Locl; R0 < = M[Locl] I2 AR0,R0; R0 < = R0 + R0 I3 AR2,R0; R2 < = R2 − R0

Let each stage take one clock cycle. What is the number of clock cycles taken to complete the above sequence of instruction starting from the fetch of I1?

  1. 8

  2. 10

  3. 12

  4. 15

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B Correct answer
Explanation