Past exam of the year 1 of the computer science course of the University of Oxford / 2016 / Digital systems, linear algebra, introduction to formal proof (resit) / 3 / c / Solution

Conditioning on a cache hit or cache miss, the expected latency isThis is a straight line from $(0,45)$ to $(1,1)$; at hit rate $1/2$, the mean is 23 ms. The 45 ms is already the complete miss-service time in the question, so another cache-lookup millisecond is not added to it.