If the ALU operation can be shortened by 25% will it affect the speedup obtained

Question

If the ALU operation can be shortened by 25% will it affect the speedup obtained from pipelining? If yes by how much? (explain your answer in no more than 5 lines) What if the ALU operation took 20% more time, will it affect the speedup obtained from pipelining? If yes by how much? (explain your answer in no more than 5 lines) Given the time series diagram below: If the ALU operation can be shortened by 25% will it affect the speedup obtained from pipelining? If yes by how much? (explain your answer in no more than 5 lines) What if the ALU operation took 20% more time, will it affect the speedup obtained from pipelining? If yes by how much? (explain your answer in no more than 5 lines)

Explanation / Answer

a.
Even if the ALU operation is shortened by 25 % , there will be no affect on the speedup obtained from pipelining,as the length of the longest stage remains the same , because remaining stages like IF and MEM still take 200 ps according to the question

b.
Now, if the ALU operation is increased by 25 % , then yes speedup will be effected ,as the the length of the longest stage will be equal to the ALU stage i.e 200ps + 25% of 200 ps = 250 ps

Therefore,

the old single cycle instruction latency = 200 + 100 + 200 + 200 + 100 = 800 ps

old speed up = 800 ps / 200 ps = 4

the new single cycle instruction latency = 200 + 100 + 250 + 200 + 100 = 850 ps

new speed up = 850 ps / 250 ps = 3.4

Therefore, the pipeline speedup is reduced from a factor of 4 to a factor 3.4

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.