(a) Consider the table shown below describing data obtained after executing a pr
ID: 3802471 • Letter: #
Question
(a) Consider the table shown below describing data obtained after executing a program P on two different processors. i. One fallacy/pitfall is to consider that the CPU with the highest operating frequency will always yield the lowest execution time for program P. Compute the execution time of program P on each CPU and use the answers to check if it is true. ii. Another fallacy is to consider that the CPU executing the largest number of instructions will require more time to execute program P. Considering that CPU A is executing a sequence of 1M instructions and that the CPI of CPUs A and B don't change, compute the number of instructions that CPU B can execute in the same time that CPU A executes 1M instructions. iii. A common fallacy is to use the MIPS rating of two different CPUs to compare their performance, where it is assumed the CPU with the highest MIPS rating is the best performing CPU. Check if this is true for CPU A and CPU B.Explanation / Answer
Answer-One usual fallacy is to consider the computer with the largest clock rate as having the large perfonl1ance. Check if this is true for PI and P2.
Number of instructions = 106
Tcpu (P1) = 106 × 1.25/4 × 10^9 = 0.315 × 10–3 s
Tcpu (P2) = 106 × 0.75/3 × 10^9 = 0.25 × 10–3 s
Clock rate (P1) > clock rate (P2), but performance (P1) < performance (P2)
Answer-2 Another fallacy is to consider that the processor executing the largest number of instruction will need a larger CPU time. Considering that processor PI is executing a sequence of 106 instructions and that the CPI of processors PI and P2 do not change, detenl1ine the number of instructions that P2 can execute in the same time that PI needs to execute 106 instructions.
P1: 106 instructions, Tcpu (P1) = 0.315 × 10–3 s
P2: Tcpu (P2) = N × 0.75/3 × 109
N = 1.26 × 106
Answer-3 A common fallacy is to use MIPS (millions of instructions per second) to con1pare the performance of two different processors, and consider that the processor with the largest MIPS has the largest perforn1ance. Check if this is true for PI and P2.
MIPS = Clock rate × 106 /CPI
MIPS (P1) = 4 × 10^9 × 10–6/1.25 = 3200
MIPS (P2) = 3 × 10^9 × 10–6/0.75 = 4000
MIPS (P1) < MIPS (P2), performance (P1) < performance (P2) in this case
Another common performance figure is MFLOPS (millions of floating-point operations per second), defined as
MFLOPS = Number of FP operations/(execution time x 10^6)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.