University of Pennsylvania-CIS 501midterm13-solutions-REVIEWED BY EXPERTS 2021-ALL ANSWERS CORRECT

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1. [ 12 Points ] Technology & Energy (a) What is Moore’s Law? Answer: [2 points] Moore’s Law states that the number of transistors per chip (or devices per integrated circuit) will double every... 1-2 years. -1 for stating > 2 years (b) Why does parallelism increase energy efficiency? Answer: [2 points] Parallelism allows a fixed computation to run at a lower clock frequency but still finish in the same amount of time as a serial execution running at high frequency. Running at lower frequency allows a processor to run at lower voltage, resulting in a cubic energy savings in dynamic power and linear savings in static power. -1 for not stating running at lower frequency (c) What does DVFS stand for? What is it used for? Answer: [2 points] DVFS, or Dynamic Voltage and Frequency Scaling, is a technique that allows a processor to run at slower speed but with less power consumption. Typically a wide range of voltage/frequency settings are supported. -1 for not stating what DVFS is -1 for not defining DVFS correctly (d) Suppose that Dennard Scaling had not stopped in 2005. What are two aspects of processor design that would likely be different today? Answer: [4 points] Processors would likely not have multiple cores and would run at much higher clock frequencies. -2 for not mentioning the lack of multi-core -2 for not mentioning higher frequency or power consumption (e) Suppose a new battery technology emerges tomorrow with an energy density 1,000x higher than today’s batteries. A chip designer proposes a new smartphone processor that runs at 10GHz since energy is no longer a concern. Is this a good idea? Why or why not? Answer: [2 points] No, barring some equivalent breakthrough in heat dissipation or transistor technology, a 10GHz smartphone processor would be far too hot to use. 1 if mentioned memory wall, 0 otherwise [Show More]

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