A 256 Mb DRAM is organised as a 32M × 8 memory externally and as a 16K × 16K square array internally. Each row must be refreshed at least once every 50 ms, and refreshing one row takes 100 ns. What fraction of the total memory bandwidth is lost to refresh cycles?
Pick an option to check yourself, or open the answer below.
Show answer & explanation
Correct answer: B. 3.3%
Explanation
Refreshing all 16,384 rows takes 16,384 × 100 ns ≈ 1.64 ms per 50 ms, i.e. about 3.3% of the time.More Computer System Architecture questions
- The instruction LD ADR(X), equivalent to AC ← M[ADR + XR], is in:
- The instructions ADD R1, A, B ADD R2, C, D MUL X, R1, R2 evaluate X = (A + B) * (C + D) using which of the following?
- The Boolean expression for F(A, B, C) = Σm(0, 2, 6) with don't-cares d(A, B, C) = Σ(1, 3, 5) would be:
- A computer system has a cache access time of 100 ns, a main-memory access time of 1100 ns and a hit ratio of 0.9. The average access time w…
- Match List I (Boolean expression) with List II (dual of the Boolean expression)List I List II A. x·y + 0 I. (x̄ + 0)·(ȳ·z) B. x̄·1 + (ȳ + z…
- The I/O method in which memory addresses and I/O addresses are distinct is called A. Isolated I/O B. Memory-mapped I/O C. Strobe control D.…