Question

1. (20pts each) Read the following set of instructions, and answer questions.

1. add     r5, r2, r1
2. lw      r3, 4(r5)
3. or      r3, r5, r3
4. sw      r3, 0(r5)
5. add     r2, r5, r1

Assume there are no forwarding, try reorganize the order of these instructions such that these 5 instructions can be finished sooner. Insert stall cycles only when reordering does not help. Note that reordering instructions should not cause any incorrect value being write into registers. Show the reordered 5 instructions, and the result in multiple-cycle diagram.

Answer 1

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Step 2

5 stage pipeline

IF --- Instruction Fetch

ID----- Instruction Decode

EX ---- Execution

MA------ Memory Access

WB ----- Write Back