Answer :
These hazards, efficient instruction-level parallelism can be achieved, optimizing the performance of the pipeline.
a) **Data dependencies** occur when the execution of one instruction depends on the result of a previous instruction. In the given assembly code, the following dependencies can be identified:
1) **Read-after-write (RAW)** dependency: Instruction 2 (AND) depends on the result of Instruction 1 (OR), specifically the value in register x1.
2) **Write-after-read (WAR)** dependency: Instruction 3 (SUB) depends on the result of Instruction 2 (AND), specifically the value in register x1.
3) **Write-after-write (WAW)** dependency: Instruction 7 (XOR) depends on the result of Instruction 6 (ADD), specifically the value in register x4.
4) **Read-after-write (RAW)** dependency: Instruction 8 (SW) depends on the result of Instruction 6 (ADD), specifically the value in register x8.
b) In the **OTTER five-stage pipeline**, the RAW dependencies identified in part (a) become hazards. Hazards occur when instructions are dependent on each other and require data that is not yet available in the pipeline. RAW hazards cause stalls or pipeline bubbles, where instructions are delayed to ensure data dependencies are satisfied. In this case, Instruction 2 (AND) would need to wait for the result of Instruction 1 (OR), Instruction 3 (SUB) would need to wait for the result of Instruction 2 (AND), Instruction 7 (XOR) would need to wait for the result of Instruction 6 (ADD), and Instruction 8 (SW) would need to wait for the result of Instruction 6 (ADD).
c) Other types of hazards possible when using **instruction-level parallelism** include:
1) **Structural hazards**: These occur when multiple instructions require the same hardware resource simultaneously. They can be resolved by resource allocation and scheduling techniques, such as ensuring that conflicting instructions do not overlap in the pipeline.
2) **Control hazards**: These occur when the outcome of a branch instruction is not yet determined, leading to potential incorrect fetch and execution of subsequent instructions. They can be resolved through techniques like branch prediction or branch delay slots.
3) **Output hazards**: These occur when multiple instructions attempt to write to the same register simultaneously. They can be resolved by forwarding or bypassing techniques, where the result of an instruction is directly forwarded to subsequent dependent instructions, avoiding the need to wait for the value to be written to a register.
By identifying and mitigating these hazards, efficient instruction-level parallelism can be achieved, optimizing the performance of the pipeline.
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