A cache line is 64 bytes. The main memory has latency 32ns and bandwidth…
2006
A cache line is 64 bytes. The main memory has latency 32ns and bandwidth 1G.Bytes/s. The time required to fetch the entire cache line from the main memory is
Answer: C. 96 ns — Key idea: total time to fetch a cache line = memory latency + transfer time to move the cache line. Step 1: Compute transfer time. Transfer time = 64 bytes /…
- A.
32 ns
- B.
64 ns
- C.
96 ns
- D.
128 ns
Attempted by 96 students.
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Correct answer: C
Key idea: total time to fetch a cache line = memory latency + transfer time to move the cache line.
Step 1: Compute transfer time.
Transfer time = 64 bytes / 1 GByte/s = 64 / 1,000,000,000 s = 64 ns.
Step 2: Add the memory latency.
Total time = 32 ns (latency) + 64 ns (transfer) = 96 ns.
Answer: 96 ns to fetch the entire 64-byte cache line.
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