What is the geometric mean of the values 4, 2, 4, 82? 8. Suppose a computer spen

Question

What is the geometric mean of the values 4, 2, 4, 82?

8. Suppose a computer spends 90 percent of its time handling a particular type of computation when running a given program, and its manufactures make a change that improves its performance on that type of computation by a factor of 8.5. If the program originally took 100s to execute, what will its execution time be after the change?

9. A computer architect is designing the memory system for the next version of a processor. If the current version of the processor spends 80 percent of its time processing memory references, by how much must the architect speed up the memory system to achieve an overall speedup of 1.2?

10. What are the differences between IPC/CPI, MIPS and benchmark suit? Explain which one is the best performance metric and why?

Explanation / Answer

Hi

10 answer -

Difference between IPC and CPI :

The Number of clock cycles required to execute each instruction,

CPI = The number of clock cycles required to execute the program / number of instructions executed in running the program

Both metrics give the same information & the choice of which one to use is generally made based on which of the values is greater than the number 1

For systems that can execute more than one instruction per cycle, the number of instructions executed per cycle, or IPC often used instead of CPI

Say there is a loop with 80 instruction executed 42 times and a total of 10,000 cycles were taken to execute the program, so ,

the total executed instructions = 80 x 42 = 3360

modern (intel)superscalar CPUs retire 4 instruction per cycle (IPC); so ideal CPI for modern processors = 1/4 = 0.25 . So by comparing ideal and actual , you can know that your code might be stalling & is unable to harness the computing resources within the Processor!

Thanks

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