8. A hierarchical memory system that uses cache memory has cache access time of 50 nano seconds, main memory access time of 300 nano seconds, 75% of memory requests are for read, hit ratio of 0.8 for read access and the write-through scheme is used. What will be the average access time of the system both for read and write requests ?
Explanation:
The average access time of the system for memory read cycle is
0.8×50+0.2×350=110ns
The average access time of the system for both read and writes request is
0.75×110+0.25×300=82.5+75=157.5