Which of the following are NOT true in a pipelined processor? I. Bypassing can…
2008
Which of the following are NOT true in a pipelined processor?
I. Bypassing can handle all RAW hazards.
II. Register renaming can eliminate all register
carried WAR hazards.
III. Control hazard penalties can be eliminated by
dynamic branch prediction.- A.
I and II only
- B.
I and III only
- C.
II and III only
- D.
I, II and III
Attempted by 129 students.
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Correct answer: B
Answer: Statements I and III are NOT true; statement II is true.
Statement I: Bypassing (forwarding) cannot handle all Read-After-Write (RAW) hazards. It forwards results from later stages, but cases like a load-use hazard require the loaded data from memory and often need an extra stall cycle.
Statement II: Register renaming does eliminate register-carried Write-After-Read (WAR) hazards by assigning different physical registers to logically distinct values, removing false dependencies.
Statement III: Dynamic branch prediction reduces control hazard penalties on average but cannot eliminate them entirely. Mispredictions still cause pipeline flushes and recovery penalties.
Therefore, the statements that are NOT true are I and III only.