Question

Consider a paging system with a page table stored in memory where memory reference takes 200 nanoseconds and all pages are in memory.What is the effective memory reference time if the hit ratio for the associative registers is 70%, the hitratio for memory is 20%, and 10% of the time we must go out to the disk to load the faulted page inmemory, where context switching, disk transfer time, etc takes 100 nanoseconds.).

Answer 1

A great Question.

first subtract referencing and another constant time units that is 200 -100 =100 ns

now hit ratios are 70% that is there is 30% chance it will fail. Since registers are fast. lets say avg time will be 70% of 10ns which is 7ns.Then in 7ns multiplied by 20% and 10 % that comes out to be 35 ns therefore, average time will be 75 ns