Q. 17 A computer system has an L1 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.
When there is a miss in both L1 cache and L2 cache, first a block is transferred
from memory to L2 cache, and then a block is transferred from L2 cache to L1
cache. What is the total time taken for these transfers ?
(A) 222 nanoseconds
(B) 888 nanoseconds
(C) 902 nanoseconds
(D) 968 nanoseconds
Answer: (c)
Explanation:
