Memory Hierarchy Q.72
A computer system has an L1 and L2 cache, an L2 cache, and a main memory unit connected as shown below. The block size in L1 cache is 4 words. The block size in L2 cache is 16 words. The memory access times are 2 nanoseconds, 20 nanoseconds and 200 nanoseconds for L1 cache, L2 cache and main memory unit respectively.
- Option : D
- Explanation : Since the block size of L2 cache is 16 words and
the bandwidth of main memory * L2 cache is 4
words, it requires a transfer of 4 words 4 times
and then a transfer of required 16 words from L2
cache to L1 cache.
So total time is 4 * (200 + 20) + 4 * (20 + 2)
= 968 nano seconds.
