Assuming that the hot ratio of the cache memory is 90% and the hit ratio of RAM
ID: 3541991 • Letter: A
Question
Assuming that the hot ratio of the cache memory is 90% and the hit ratio of RAM (if missed by cache) is 80%, and the processing of each instruction requires 4 lookup on an average. Also assume that only 30% of the data can be stored in the data registers, and remaining has to be retrieved from cache, RAM, or harddisk. Also assume that the register lookup takes 5 ns, cache memory lookup takes 30 ns, and RAM look up is 200 ns, and time taken to load a page (including page table lookup) from disk is 3 ms. How much time on an average it would take to look up a data element for a program that executes 200 million instructions.
Explanation / Answer
Total time =
(200 * 10^6 * 4 * (0.30 * 5 ns + 0.70 * (0.90 * 30 ns + 0.10 * 0.80 * (200 + 2*30) + 0.10*0.20*3000000 ))) / 1000000000
= 33627.968 sec