ITPEC FE Morning April 2022 Question 11
ITPEC FE Morning April 2022 — Question 11 of 80
CPI (Cycles Per Instruction) — calculate average cycles per instruction from clock rate and execution speed.
Formula: CPI = clock_rate / instructions_per_second
Given:
- Clock rate = 2.4 GHz = 2.4 × 10⁹ cycles/sec
- Execution speed = 1 billion = 1 × 10⁹ instructions/sec
Calculation:
- CPI = 2.4 × 10⁹ / 1 × 10⁹ = 2.4
Answer: (c) 2.4
Why not others:
- (a) 0.04 — would imply far more instructions per cycle than the clock allows
- (b) 0.12 — incorrect arithmetic; no combination of given values produces this
- (d) 25 — would require a much slower execution rate relative to clock speed
Key rule: CPI = clock_rate ÷ execution_rate when both are in the same units (e.g., GHz and GIPS). Higher CPI means more cycles wasted per instruction.
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