please help: It is multiple choice question, so which of the following 5 choices

Question

please help: It is multiple choice question, so which of the following 5 choices is the correct answer??

Consider executing each of the code sequences on the pipelined MIPS implementation Also consider executing them on this design with value forwarding logic and datapaths added. Which of the following statements best describes how the forwarding logic would alter the execution times?

1- Neither (A) nor (B) is affected by forwarding
2- Both (A) and (B) would be faster using forwarding
3- (A) would be faster using forwarding, (B) is not affected
4- (A) is not affected, (B) would be faster using forwarding
5- The execution time improvements due to forwarding depend on the values in the registers, not on the instructions being executed; thus, it is impossible to say how execution times for (A) and (B) are affected

Explanation / Answer

There is a true dependence between lw and both the sw and beq in (A); although (B) has an anti-dependence on $t0, it has no true dependences that could cause bubbles. Forwarding simply reduces the size of the bubble caused by a true dependence.

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