Question

Assume that for a certain processor, a read request takes 50 nanoseconds on a cache miss and 5
nanoseconds on a cache hit. Suppose while running a program, it was observed that 80% of the
processor's read requests result in a cache hit. The average read access time in nanoseconds is
__________.

Answer 1

The Answer Is 14.....

Answer 2

The average read access time in nanoseconds is 14 Nanosecond

Explanation :

Given that 80% of the processor's read request results in cache hit = 0.8

time taken to process a cache hit = 5 nanosec

=> Avg time taken to process a cache hit = 5 x 0.8 = 4 nsec

read request results in cache miss = 1 - 0.8 = 0.2

time taken to process a cache miss = 50 nanosec

=> Avg time taken to process a cache miss = 50 x 0.2 = 10 nano sec

Hence The average read access time in nanoseconds is

= 4 + 10

= 14 Nanosecond