Assignment 6: Power & Performance

Assigned: Tuesday, October 4

Due: Wednesday, October 12 at the beginning of class

Submitting your work: Please submit a hard copy of this assignment in class.

Overview

We’ll have many opportunities to practice using MIPS assembly in lab and during class, but we haven’t spend much time on power and some of the details of MIPS execution. This assignment will cover power, performance, and some less-common MIPS instructions.

Collaboration

Please complete this assignment individually. You may discuss the assignment with other students, provided you do not discuss your solutions.

What to turn in

Hand in your answers, along with all written work. Make sure you show the process you used to derive your answers, including appropriate units next to every number in both your solution and work.

Problem 1

Complete the following problems from our textbook (4th edition, revised printing):

Exercise 1.3.1
Exercise 1.3.2
Exercise 1.3.3

Warning: The problems in the 4th edition of the textbook are different from the 4th edition “revised printing.” You should complete the problems in the revised printing.

Problem 2

Assume that a given program can be parallelized to run on 1, 2, 4, or 8 cores, but running the program in parallel requires some additional instructions to coordinate across cores. The table below shows the number of instructions that must be executed on each core for a given number of cores.

Cores	Instructions per core
1	$$1 \times 10^{10}$$
2	$$6 \times 10^9$$
4	$$4 \times 10^9$$
8	$$3 \times 10^9$$

Assuming a 3.9GHz clock frequency and an average CPI of 1.2, what is the program execution time in each scenario?
Recall that the power consumption of a processor core is $\text{P} = C \cdot V^2 \cdot f$ , where $P$ is power in Watts, $C$ is capacitance in Coulombs per Volt, $V$ is voltage, and $f$ is frequency in Hertz. Find the cumulative power consumption of the program in each scenario, assuming that each core runs at 4GHz, has a capacitance of $2 \times 10^{-9} \dfrac{C}{V}$ , and has a voltage of $1.75V$ .
Suppose we “downgrade” the system to 2GHz processors. What is the program execution time and power consumption in each scenario now?

Problem 3

Complete the following problems from our textbook (4th edition, revised printing):

Exercise 2.13.2 a and b
Exercise 2.14.1 a and b
Exercise 2.15.2 a and b

Warning: The problems in the 4th edition of the textbook are different from the 4th edition “revised printing.” You should complete the problems in the revised printing.