Answer:
B) 2.22
Explanation:
In a first step, the system will look in cache number 1. If it is not found in cache number 1, then the system will look in cache number 2. Finally (if not in cache 2 also) the system will look in main memory.
The average access time will take into consideration success in cache 1, failure in cache number 1 but success in cache number 2, failure in cache number 1 and 2 but success in main memory.
Mathematically we can write it into the following equation :
Where AAT is the average access time
H1,H2 and Hm are the hit rate of cache 1,cache 2 and main memory respectively.
T1,T2 and Tm are the access time of cache 1, cache 2 and main memory respectively
Hm = 1
Therefore, option b) is the correct.
