CS 429: Fall, 2019
Computer Organization and Architecture

Instructor: Dr. Bill Young

Unique numbers: 50300, 50305, 50310; Class time: MTWTH 2-4pm; Location: UTC 3.122
Unique numbers: 50315, 50320; Class time: MTWTH 4-6pm; Location: UTC 3.122
Instructor Office: GDC 7.810; Phone: 471-9782; Email: byoung at cs.utexas.edu
Instructor Office Hours: Mondays 9-11am and by appointment
TA: Adrian Trejo; Email: atrejo at cs.utexas.edu; TA Office Hours: Tues. and Thurs. 10-11am in GDC 4.416.
TA: Henrique Fingler; Email: hfingler at cs.utexas.edu; TA Office Hours: Mon. and Wed. 12:30pm-1:30pm
Proctor: Matthew Hinton; Email: mjh4395 at utexas.edu; Proctor Office Hours: Tues. and Thurs. 2-3:30pm, 3rd floor computer lab
Proctor: Chandler Ochs; Email: chandlerochs at yahoo.com;
Proctor Office Hours: Tues. 4-6pm and Thurs. 11am-1pm, GDC basement (desk 2 or 3)
Proctor: Jennifer Suriadinata; Email: jsuriadinata at utexas.edu; Proctor Office Hours: Wed. 1-2pm and 6-7pm, location TBA
Proctor: Sooyong Lee; Email: sooyonglee1 at gmail.com; Proctor Office Hours: Mon. and Wed. 8-9am and Mon. 11am-noon, GDC basement desk 5
This website: www.cs.utexas.edu/users/byoung/cs429/syllabus429.html

Important Class Announcements:

Breaking news important to the class will be posted here. Consult this spot often.

Fifth weekly homework is here: HW5: due 10/11. Fourth weekly homework is here: HW4: due 10/4. Some of these problems mentioned using a union to make it easy. Here's an example: union example

Exam1 has been graded; you can find your grade on Canvas. Stats are here: Exam1 statistics.

Here is the study guide for Exam1: Study Guide

Here is your third weekly homework: HW3. It's due Friday, 9/27, by midnight.

After consultation with the TAs, we've decided to trim the Friday discussion sections a bit. They'll meet from 10am - 2pm in UTC 1.116. Recall that you can come any time during that period; you don't have to come at the time for which you registered. Also, they'll mainly be help sessions. There won't be lectures or quizzes or anything like that during the discussion sections. Please let me know ASAP if there's some reason this won't work for you.

Here is the second weekly homework: HW2. It's due this Friday, 9/20, by midnight.

We'll be programming in C this semester. The following as a pretty good style guide to follow in all of your assignments: style guide. We probably won't grade as strictly as defined by this webpage, but it will provide you with guidelines on how to write rigorous C and settle any "what are the style guidelines" questions.

Dr. Young's office is in the south wing. You have to take the south elevator, because the two towers don't connect on the 7th floor.

Feel free to email me (Send me an email message), but please put "CS429" in the header.

Course Description:

CS429 is the first course in the systems core sequence required of all UT CS majors. It describes how computers operate at a fairly low level of abstraction. For example, we'll consider: Understanding these fundamentals thoroughly is absolutely essential to your future success in computer science. The material of this course is quite detailed and requires careful and diligent study. If you are not willing to put in the time and effort required to master this material, you probably should reconsider your decision to major in Computer Science.

The UT College of Natural Sciences recently published Vision and Recommendations for 21st Century Undergraduate Education (June, 2016). It contains these words:

"Research on learning shows that transformative education requires teaching methods that engage students in productive intellectual struggles. Students must personally grapple with scientific and mathematical concepts to develop a deep understanding of core principles. They must be given opportunities to overcome obstacles and failure to develop an acceptance of ambiguity and a willingness to persevere."
In this class, you won't succeed unless you do some struggling, grappling and persevering, and accept ambiguity! Not everything will be spelled out for you and there are a number of skills you'll have to acquire on your own. You will be asked to complete some very challenging assignments. In some cases you will be expected to use tools and techniques that are not discussed in class. That is not to say that help is not available; just that we expect you to be proactive about learning. This is a skill you must acquire now, because you'll need it for your entire academic and professional career. Toto, I don't think we're in high school anymore!

The students that do well in this class are survivors. This class is a lot of work, and it is important to keep current. The material in this class is cumulative; it can be quite difficult to catch up if you fall behind. It is important to keep turning in homework and coming to class. Here are some general hints for succeeding in this and other classes: Hints for Success.

We will be discussing several different programming languages in this course: C, x86 assembly language, and Y86 assembly language. You will be writing programs in at least C and x86.

If you want to get a sense of what this course is like, I suggest you watch this short video: An Apt Metaphor for CS429.

Weekly Discussion Sections:

After consultation with the TAs, we've decided to trim the Friday discussion sections a bit. They'll meet from 10am - 2pm in UTC 1.116. Recall that you can come any time during that period; you don't have to come at the time for which you registered. Also, they'll mainly be help sessions. There won't be lectures or quizzes or anything like that during the discussion sections.

Using Piazza:

We will be using Piazza for class communication. The Piazza system is highly catered to getting you help quickly and efficiently from classmates, the TAs, and myself. Rather than emailing questions to the teaching staff, I encourage you to post your questions on Piazza. Don't post code and other items on Piazza that give away solutions to homework or labs, unless you post them privately (visible only to yourself and the instructors.)

If you turn off Piazza notifications and miss an important posting, you are responsible. If you have any problems or feedback for the developers, email team at piazza.com. Because of some issues in past semesters, posts may be anonymous to the class, but not to the instructors. I expect that posts will be pertinent and respectful. Don't use Piazza as a place to vent or trash anyone. Please don't waste everyone's time posting jokes and other fluff.


You are expected to have taken and passed the following courses (or equivalent) with a grade of at least C-: Computer Science 311 (or 313K) or 311H (or 313H); and Computer Science 314 (or 315) or 314H (or 315H). If you don't have the prerequisites, be sure to clear it with the CS department or risk being dropped from the class.


The required text book for this class is Computer Systems, A Programmer's Perspective by Randal E. Bryant and David O'Hallaron, Prentice Hall, 2016 (Third Edition). You must have the 3rd edition, which is substantially different from the 2nd edition. It's up to you to be sure you have a correct edition. Note that this book is also used in CS439, so don't sell it back at the end of the semester if you plan on continuing in CS.

There is an available international edition that costs less than the standard edition. But be aware that some of the homework problems appear to be different in the international edition. So make sure that if you buy the international edition, that you check with someone who has regular book to make sure you're doing the right problems.

There is apparently also an ebook version here which you are welcome to investigate: eBook version.

Note that our book has quite a few errors. You can find the errata here: book errors. Several times, I've been puzzled by something in the book only to find that it was wrong.

Since we will be programming some in C, I recommend that you have access to The C Programming Language, second edition, by Brian Kernighan and Dennis Ritchie, Prentice Hall Software Series. This is available on-line. There are also many Web pages devoted to C-language programming. A nice tutorial intro to C is here: C Tutorial. Java programmers should have no problem with the subset of C that we will use.

Class Schedule and Slides:

The class schedule is here: schedule. This schedule is approximate; some dates may change. Rely on the assignment handouts, not on this schedule for assignment due dates.

All of the class slides will be made available via links below as we cover new material. You are welcome to print them out or view them on-line. Slides are in PDF form. They are derived from slides originally developed for the course by Bryant and O'Hallaron and substantially modified by me and other professors. They are used with permission.

The following is a tutorial on C generated by a UT grad student: C Tutorial

Slides on C: 4up-PDF  PDF

Slideset 1: Introduction to Computer Systems 4up-PDF PDF

Slideset 2: Bits and Bytes 4up-PDF PDF

Slideset 3: Integers 4up-PDF PDF

Number wheel for unsigned 4-bit ints: Unsigned.

Number wheel for signed 4-bit ints: Signed.

Slideset 4: Floating Point 4up-PDF PDF

Slideset 5: Digital Logic 4up-PDF PDF

Exam1 will cover through Slideset 5.

Slideset 6: ISA I 4up-PDF PDF

Slideset 7: ISA II 4up-PDF PDF

Slideset 8: ISA III 4up-PDF PDF

Slideset 9: ISA IV 4up-PDF PDF

Slideset 10: ISA V 4up-PDF PDF

Slideset 11: ISA VI 4up-PDF PDF

No Laptops:

If you want to use laptops, cell phones, or other electronic devices, please step out of the class. In previous semesters I've had complaints from students that use of laptops was distracting to other students. And if you're using your cellphone during class, you'll distract me.


For the past several semesters, I have been making some videos that you might find helpful. Generally, they cover small snippets of class material that some students find confusing. If you have other topics for which you'd find such videos helpful, please share them with me.

Same Bits, Different Interpretations
Big Endian vs. Little Endian
Representing Unsigned Integers
Representing Signed Integers
Why Sign Extension Works
Representing Normalized FP Numbers
Representing Denorms and Special FP Values
Round to Even
Multiplying Floating Point Numbers
Adding Floating Point Numbers
Functionally Complete Sets of Boolean Operators
Assembly Language Programming: Swap
x86 Push instruction
x86 Pop instruction
x66 Call and Ret instructions
Using x86 Condition Codes
Array Indexing
Handling Data Hazards in the Y86 Pipeline
Cache Reading
Handling Cache Misses


There will be three in-class exams of approximately one and one half hours each. See the schedule for dates: schedule. There will be no makeups on in-class exams, but I will drop the lowest of these three scores. Exams are cumulative but will focus very heavily on the material since the previous exam.

The final exam is optional for anyone who has taken all three in-class exams and is willing to take the (normalized) average of all three exams as their final exam score. Our final exam is on the date and time determined by the registrar. That will be available later in the semester.

We will have a combined final exam, meaning that both classes will take it at the same time. The registrar's site probably will also lists a makeup exam time. I don't plan to give the makeup, so don't plan on taking it. Since the exam is optional, you must take it on the scheduled date, if at all. However, if you have to take the exam and have a verifiable conflict with another exam, talk to me in person and we'll arrange for you to take the exam early.

Your exam grades is computed as follows: If you take all three in-class exams and are happy with the average (of all three), you can skip the final and substitute that average for the final exam score. For example, suppose you receive (normalized) scores of 100, 90, and 80 on the three exams. Your average for the in-class exams is 95 (dropping the lowest score of 80), which counts 30% of your grade. If you choose not to take the final exam, your score on that is 90 (the average of all three), which counts 20% of your grade. If you skip any of the in-class exams, you must take the final. If you do take the final, the score on that test will be your final exam score, no matter how well you did on the in-class exams. I.e., taking the final exam could lower your grade.

We also will have several pop quizzes over the course of the semester, probably every two weeks or so. They will be counted along with the 15% of your grade from weekly homeworks. There will be no makeup for quizzes, but they individually count only a small fraction of your grade, so don't freak out if you miss one. Quizzes may cover any material we've covered previously in the class, but will focus on recent material.


Written homework will be assigned nearly every week. They're due by the end of the due day (midnight). Answers must be submitted on Canvas and will not be accepted late. You may discuss written assignments with classmates and get help from the instructors; but submit your own work. This is an easy portion of your grade so make the most of it.

You will have around 6 labs over the course of the semester. You must work alone on all labs. The due dates will be clearly marked. For labs, you will have 3 grace days available which you can use over the course of the semester. If you turn in an assignment late and wish to use a grace day, just inform the lead TA for that lab. We'll keep track of how many you've used. You'd do well to save grace days as long as possible to deal with illnesses and personal emergencies.

We'll be programming in C this semester. You can use the following as the style guide to follow in all of your assignments: style guide. We won't grade as strictly as defined by this webpage, but it will provide you with guidelines on how to write rigorous C and settle any "what are the style guidelines" questions.

When you get your lab and homework grades, please check them carefully. If there's an error call it to our attention. We expect that after a week the grades will be final, unless there is a real issue.

Labs are generally posted on Canvas and Piazza.

Links to weekly homeworks will appear here and probably also in the Important Class Announcements at the top of this page. Homeworks are always due by 11:59pm on the due date.

Homework 1: due 9/17, 11:59pm

Homework 2: due 9/20.

Homework 3: due 9/27.

Homework 4: due 10/4.

Homework 5: due 10/11.

Getting help:

It is a good idea to post your questions on Piazza, so that others can comment and also see the answer. But please don't post homework or lab solutions or large code fragments except in private messages to the instructors. General questions about class material, quizzes or tests should be directed to Dr. Young. The TAs will manage and grade the labs and they are your best source of information on those. Weekly homeworks are generally graded by the proctors; direct your questions there for homeworks.


You are strongly encouraged to come to class. Attendance will not be checked, but my experience suggests strongly that students who regularly miss class do poorly. On test days, be sure to arrive on time.

Computation of Your Grade:

The weighting of the grades for the various aspects of the course are as follows:

Component Percent
In class exams (one dropped) 30%
Final Exam 20%
Homework and Quizzes15%
Labs 35%

Canvas attempts to compute a running average course grade as individual scores are entered. You should totally ignore that. I'm not making any effort to get Canvas to weight things appropriately, drop low scores, etc. If you want to know how you're doing in the class, compute the score yourself.

Grades for the entire course tentatively will be averaged using the weighting below:

Course score Grade
[90... 93)A-
[87... 90)B+
[83... 87)B
[80... 83)B-
[77... 80)C+
[73... 77)C
[70... 73)C-
[65... 70)D+
[60... 65)D
[ 0... 60)F

This is tentative. The grades may be curved and may be a bit more generous than this. They will not be less generous. That is, if you have a 93 you are guaranteed an A; but somone who gets an 92 might also get an A, depending on the final distribution of grades in the class.

A course grade of at least C- is required for this course to count toward a UT CS degree.

Scholastic Dishonesty:

Academic dishonesty will not be tolerated. See http://www.cs.utexas.edu/academics/conduct for an excellent summary of expectations of a student in a CS class.

All work must be the student's own effort. Work by students in previous semesters or code that you find on-line is not your own effort. Don't even think about turning in such work as your own, or even using it as a basis for your work. We have very sophisticated tools to find such cheating and we use them routinely. It's far better to get a 0 on an assignment than to cheat.

Apparently, many students begin every assignment by immediately going to Google, trying to find something that might keep them from having to solve the problem for themself. That is an incredibly stupid thing to do. If you as much as Google "solution to XXXLab," you're already starting down a slippery slope that's liable to send you over the edge. Suppose you find something up to and including a complete solution that some idiot has posted on GitHub; it will be too tempting not to use it. You may naively believe that changing variable names and reordering code will keep you from being caught. With very high likelihood, that's not true. Every semester, students learn this the hard way. It's just not worth it!

Remember the lesson of Virginia Attorney General Mark Herring. In 1980, as a 19 year old college student, Herring wore blackface to a party. In 2019, 39 years later, that one stupid adolescent decision almost cost him his career. Stupid things you do now can affect you for the rest of your life! Getting caught cheating is one of those things that can haunt you forever. Don't do it!

Also, don't post your work on any publicly available site, such as GitHub or Course Hero. It's understandable that you're proud of your work, but this just invites copying for students this semester and in subsequent semesters. If someone copies your work, even without your knowledge, you will both be liable to punishment, even in subsequent semesters. Here's what Mike Scott said when I mentioned this issue to him:

I have submitted cases to Student Judicial Services for past students who have posted code from CS314 and CS312 to public repos and current students used it to cheat. Not much SJS can do grade wise, but it is recorded and they often have to write an essay about the matter.
I plan to follow Mike's lead here. There are other services such as BitBucket that have private repositories; you can grant selective access to instructors and to potential employers.

Also, don't repost my slides or any other class materials on CourseHero or any other public repository. Consider all course materials to be copyright. You can get into serious legal problems violating copyright laws, and you will certainly have problems with me if you do this.

No deviation from the standards of scholastic honesty or professional integrity will be tolerated. Scholastic dishonesty is a serious violation of UT policy; and will likely result in an automatic F in the course and in further penalties imposed by the department and/or by the university. Don't do it! If you are caught, you will deeply regret it. And even if you're not caught, you're still a cheating low-life.

Students with Disabilities:

Students with disabilities may request appropriate academic accommodations from the Division of Diversity and Community Engagement, Services for Students with Disabilities, 471-6259, http://www.utexas.edu/diversity/ddce/ssd.

Typically, students allowed extra time or a quiet testing environment will take exams in a conference room on GDC 7 South at the same time as the regular exam. The TA or proctor will supervise the exam. If you are allowed such accommodations, be sure to get me your SSD letter well in advance of the test since I will need to arrange a TA to proctor your test. Please be flexible with respect to time, etc.

Grad Students Clearing Architecture Background Requirement

If you're a grad student who needs to complete your background requirement in Architecture by exam, I'm happy to help you with that. You can do as little as take the final exam for CS429 with a grade of at least 80%. But be aware that the exams for this class (or any class) are idiosyncratic and assume that the person taking the test is also taking the class. For example, we focus on the x86 ISA. You could be a world-class expert on the MIPS or ARM architecture and not do well on the exam. My suggestion is to study the appropriate sections of the Bryant and O'Hallaron book, review the class slides, and take the three in-class exams. BTW: the final is optional for students in the class who take all three in-class exams. I'll give you the same option. If you get 80% average on the three in-class exams, I'll count that as clearing your background requirement. That's probably much safer than rolling the dice and just taking the final.

Some Interesting Links:

As I find items of interest to the class, I post them here. Newer items are near the top.

Found this nice "cheatsheet" on x86-64: X86 ref.

Nice Reference on x86 Instructions
NYT article partly on UT CS
C primer
Why 32-bit ops on registers zero the upper 32-bits
Which x86 instructions set flags?
Anatomy of Solid State Drives
Mixing C and Assembly. Note: I'm not certain all of the examples in this are correct.
Factorial Function in Assembly
Nice intro to GDB
Useful interface for GDB
gcc Optimization Levels
40 Years of the x86
C Coding Style Guide
Errata for our textbook
Using Valgrind
UT Grads Thriving
Papers on SSD
Why your tiny program gives a large executable
Compiling with gcc
Complete x86 registers
Nice x86 IA32 reference
Lucy Pipelining Example
PC-relative addressing.
x86 Instruction Manual
Comparing signed and unsigned
Resources on processors and optimization
Blog on x86 coding
How a CPU Works
Which Engineers Make the Most
Replace Hard Drives with DRAM?
CS students in demand
Layout of a Program in Memory
Disk drive at work
Cache Associativity Cartoon
Ender's Game a Reality
Status of Moore's Law
Good PDP-8 reference
IA32 cheat sheet
Primer on Y86
Decimal to FP guide
x86 Assembly Guide
Moore's Law Dead?
Unix, C Hoaxes?
5 Things to Know
Indiana U. Career Overview
Jobs Prospects
Top 10 Jobs for CS Majors
Jobs with High Pay
Cities with Most CS Jobs