A dynamic RAM has a refresh cycle of 32 times per millisecond. Each refresh…
2015
A dynamic RAM has a refresh cycle of 32 times per millisecond. Each refresh operation requires 100 ns, and a memory cycle requires 250 ns. What percentage of the memory's total operating time is required for refreshes?
Answer: D. 0.32 — Key idea: Find the total time spent on refreshes in one millisecond and express it as a percentage of 1 ms. Number of refreshes per millisecond = 32. Time per…
- A.
0.64
- B.
0.96
- C.
2.00
- D.
0.32
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Correct answer: D
Key idea: Find the total time spent on refreshes in one millisecond and express it as a percentage of 1 ms.
Number of refreshes per millisecond = 32.
Time per refresh operation = 100 ns.
Total refresh time per millisecond = 32 × 100 ns = 3200 ns = 3.2 µs = 0.0032 ms.
Percentage of operating time used for refresh = (0.0032 ms / 1 ms) × 100 = 0.32%.
The given memory cycle time is not needed for this percentage calculation. Therefore, the correct answer is 0.32%.