Neco 2023 Computer Studies Question 2

A computer system has the following specifications: - CPU clock speed: 3.2 GHz - Cache hierarchy: L1 = 64 KB (access time 1 ns, hit rate 95 %), L2 = 256 KB (access time 4 ns, hit rate 85 %), L3 = 8 MB (access time 12 ns, hit rate 70 %) - Main memory: 16 GB (access time 120 ns) - The program to be executed consists of 2.5 million instructions. Each instruction, on average, requires one data reference. Assume the CPU can execute one instruction per clock cycle when the required data is found in L1; otherwise it must wait for the data to be fetched from the next level. Answer the following: (a) Calculate the average memory access time (AMAT) for a data reference. (b) Determine the total number of CPU cycles lost because of cache misses. (c) Compute the total execution time of the program in seconds. (d) If the L2 hit rate is improved to 90 % (all other parameters unchanged), recalculate the execution time and state the percentage reduction obtained.