GATE CS 2003 Q10 — Instruction Pipelining

In a pipelined processor, hazards prevent the next instruction in the instruction stream from executing in its designated clock cycle. Let us analyze each of the given situations:

1. Situation I: The $(j+1)^{\text{th}}$ instruction uses the result of the $j^{\text{th}}$ instruction as an operand.
   This introduces a dependency where a register is read before it is written by the preceding instruction. This causes a Data Hazard (specifically, a Read-After-Write or RAW hazard).


2. Situation II: The execution of a conditional jump instruction.
   Since the target address and the branch outcome are not known immediately, the pipeline cannot confidently fetch the next instruction. This causes a Control Hazard (or branch hazard).


3. Situation III: The $j^{\text{th}}$ and $(j+1)^{\text{th}}$ instructions require the ALU at the same time.
   Because the CPU has only a single ALU, both instructions cannot use this hardware resource simultaneously. This resource conflict causes a Structural Hazard.

Since all three situations can cause a hazard, the correct option is D.