ITPEC FE Morning April 2021 Question 12
ITPEC FE Morning April 2021 — Question 12 of 80
MIPS Calculation — compute CPU performance from an instruction mix.
Given instruction mix:
- •Register to register:
0.1 µs,40% - •Register from memory:
0.3 µs,50% - •Unconditional branch:
0.6 µs,10%
Step 1 — weighted average execution time:
0.1 × 0.4 + 0.3 × 0.5 + 0.6 × 0.1 = 0.04 + 0.15 + 0.06 = 0.25 µs
Step 2 — convert to MIPS:
MIPS = 1 / 0.25 = 4
Answer: (c) 4
Why not others:
- (a) 0.04 — partial product, not the full weighted average
- (b) 0.25 — average execution time in µs, not MIPS (forgot to invert)
- (d) 25 — incorrect inversion or calculation error
Key rule: MIPS = 1 / (weighted average execution time in µs) because 1/µs = 10⁶ instructions/second = 1 MIPS.
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