If average access time of CPU is 20 ns, access time of main memory is 110 ns…
2026
If average access time of CPU is 20 ns, access time of main memory is 110 ns and the cache access time is 10 ns. What is the hit ratio?
- A.
80%
- B.
95%
- C.
90%
- D.
100%
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Correct answer: C
To find the hit ratio (h), use the average access time formula: T_avg = h * T_c + (1 - h) * T_m. Given T_avg = 20 ns, T_c = 10 ns, and T_m = 110 ns. Substitute these values: 20 = 10h + 110(1 - h). Simplify: 20 = 10h + 110 - 110h. Combine like terms: 20 = 110 - 100h. Rearrange: 100h = 90. Solve for h: h = 0.9. The hit ratio is 0.9 or 90%.