PowerPC execution width claim: Assess the statement: “A PowerPC processor can effectively execute up to ten instructions per clock cycle.” Choose the best evaluation.

Difficulty: Easy

Correct Answer: Incorrect

Explanation:


Introduction / Context:
Superscalar width indicates how many instructions a processor can issue/execute per cycle under ideal conditions. Typical desktop-class PowerPC microarchitectures (e.g., 603/604/G3/G4/G5 families) provided decode/issue widths far below ten. This question checks realism regarding execution width claims.



Given Data / Assumptions:

  • Common PowerPC cores are 2- to 4-wide issue in many generations.
  • Back-end execution units (integer, floating, load/store, branch) allow parallelism but not “ten per cycle.”
  • Marketing peak counts sometimes blend micro-ops or vector lanes, but not as ten separate scalar instructions each cycle.


Concept / Approach:
We compare the ten-per-cycle claim to documented decoder/issue widths and practical sustained IPC. Even with aggressive out-of-order execution and multiple units, reaching ten scalar instructions per cycle is not credible for these designs.



Step-by-Step Solution:

Review typical PowerPC decode/issue widths: commonly 2–4.Consider peak IPC metrics: actual sustained IPC much lower due to dependencies and cache effects.Conclude the ten-per-cycle claim is unrealistic for these cores.Thus the best evaluation is “Incorrect.”


Verification / Alternative check:
Microarchitecture references and benchmarking show IPC values well below ten; instruction issue width specifications corroborate this.



Why Other Options Are Wrong:

Correct: Not supported by core specs.Only true with simultaneous multithreading: Even SMT does not yield ten scalar instructions per cycle on these designs.Indeterminate without compiler details: Compilers affect IPC, but hardware width imposes hard ceilings.


Common Pitfalls:
Confusing vector element throughput with instruction count; conflating theoretical back-end ports with front-end decode width.


Final Answer:
Incorrect

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