HW1: Power, Energy and Performance
Note: Make reasonable assumptions where necessary and clearly state them. Feel free to discuss problems with classmates, but the only written material that you may consult while writing your solutions are the textbook, lecture notes, and lecture slides.
Problem 1: Power
For a processor running at 100% utilization at 100 W, 20% of the power is attributed to leakage. What is the total power dissipation when the processor is running at 10% utilization?Problem 2: DFS and DVFS
Consider a processor that runs at 3 GHz and 1 Volt. When running a given CPU-bound program, the processor consumes 100 W, of which 20 W is leakage. The program takes 20 seconds to execute. The processor is capable of running at different voltages and frequencies. Can you compute the following values: (i) The smallest time it takes to execute the program. (ii) The lowest power to execute the program. (iii) The lowest energy to execute the program. Assumptions: The processor is capable of executing safely at voltages between 0.8 V to 1.2 V. Voltage and frequency follow a linear relationship (i.e., if voltage doubles, frequency doubles as well).Problem 3: Performance Equation
My new laptop has a clock speed that is 20% higher than my old laptop. I run the same three binaries on both machines. Each binary runs for roughly the same number of cycles on each machine. The IPCs of the binaries are listed in the table below. What is the performance improvement provided by my new laptop?
| Program A | B | C | |
|---|---|---|---|
| IPCs on old laptop | 1.0 | 0.4 | 1.4 |
| IPCs on new laptop | 0.9 | 0.3 | 1.5 |
Problem 4: Sum of Execution Times
A 4-program benchmark suite has execution times as listed below for 3 different systems. Assume that System-A is the reference machine. How does the performance of system-C compare against that of system-B? Show this comparison for all three metrics (sum of execution times, sum of weighted execution times, and GM of execution times). Report the comparison in terms of speedup.
| Program A | Program B | Program C | Program D | |
|---|---|---|---|---|
| Exec times on System-A (seconds) | 100 | 300 | 150 | 50 |
| Exec times on System-B (seconds) | 50 | 400 | 200 | 60 |
| Exec times on System-C (seconds) | 75 | 450 | 100 | 40 |
Problem 5: Power and Energy
You have a large inventory of Intel processors that run at 3 GHz and 1 Volt, and consume 100 W (of which, 20 W is leakage) when running a given CPU-bound application. This application finishes in 100 seconds on this processor. The processor is capable of DFS and DVFS, but cannot reduce its voltage under 0.9 V. A customer places an order for motherboards that have inexpensive cooling and power delivery that can only handle a processor that runs at 40 W. How will you configure your Intel processor so that it meets these specifications and consumes as little energy as possible for the same CPU-bound application? How much energy does the processor consume to finish this application on this new system?Submit your work
Submit your solution through Gradescope HW1 (as a PDF file (please mark which parts of the PDF are used for each question (this can be done through Gradescope)).
Updated: January, 2019