Question

Machine M has a clock whose period is 4 nanoseconds and three types of instructions – type A instructions that take 4 cycles to execute, type B instructions that take 4 clock cycles to execute, and type C instructions that take 2 clock cycles to execute. Program P consists of 30 instructions of type A, 25 instructions of type B, and 50 instructions of type C. What is the execution time of program P?

Answer 1

Number of cycles required to execute program P = number of instructions of type A * number of cycles required to complete 1 A instruction + number of instructions of type B * number of cycles required to complete 1 B instruction + number of instructions of type C * number of cycles required to complete 1 C instruction

= 30 * 4 + 25 * 4 + 50*2

= 120 + 100 + 100

= 320 cycles

Required execution time = Number of cycles required to execute program P * 1 cycle time

= 320 * 4 ns

= 1280 ns

= 1280 * 10^-9 s

= 1.280 microseconds

So, execution time of program P = 1280ns = 1.28 microseconds