8. State whether each of the following statements is true or false and briefly e

Question

8. State whether each of the following statements is true or false and briefly explain your answer. A correct answer with no explanation is worth only 2 points. A correct answer with an incorrect explanation is worth 0. (a) Software scheduling can reduce the number of stalls only if the processor's pipeline does not support data forwarding. (b) A pipeline that does not support data forwarding still needs to compare register fields in different instructions currently executing in the pipeline. (c) An ARM-like processor has an 8-stage pipeline consisting of the stages IF1, IF2, ID, IS, EX1/MEM1, EX2/MEM2, EX3/MEM3, WB where all instructions require the use of the three EX/MEM cycles, will never have WAW hazards but may experience WAR hazards.

Explanation / Answer

a)

This statement is false, data forwarding helps in minimizing the stalls and used for optimizations.

b)

This statement is true.

c)

False, ARM like processors have 6 stage pipelining implemented

d)

False, With the different benchmark MIPS will change

here is an example

a)

Million instructions per second(MIPS)

44% are ALU instruction which takes 1 cycle to execute

CPI= 0.44 * 1 + 0.56 * 2= 1.56

to execute one instruction it will take 1.56/10^9= 1.56 ns

MIPS= 1/1.56 * 10^9= 641.025641026 MIPS

b)

Here the benchmark is changed and the compiler is optimized ALU by 25% and all other instructions by 12.5%.

So CPI of optimized compiler is

0.44 * 0.75 * 1 + 0.56 * 0.875 * 2= 1.31

now the new MIPS is= 1/1.31 * 10^9= 763.358778626.

Yes MIPS is an acceptable metric of performance.

e)

True, if A has deeper pipeline than processor B.

I hope this helps if you find any problem. Please comment below. Don't forget to give a thumbs up if you liked it. :)

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