CS447: Computer Organization & Design

1. Welcome! CS/COE 0447 Jarrett Billingsley

2. Administrivia CS447

3. hi • you can just call me Jarrett • jarrett@cs.pitt.edu • pitt.edu/~jfb42 • I send announcements through courseweb which come thru email • announcements/grades are the only things I use courseweb for • everything else is on my site. • also computers suck and the people who work with computers suck and get out while you can. • go grow plants. CS447

4. Textbook (optional) • Computer Organization & Design (Patterson & Hennessy) • textbooks are a racket • pirate everything you can • 5th edition is stupid ("PostPC" crap) CS447

5. Grading • there is no such thing as attendance • labs: 10% • graded on effort/completion • projects: 50% • two in MIPS assembly language, one in Logisim • lowest grade worth 10%; other two worth 20% • exams: 40% • lowest grade worth 15%, other 25% CS447

6. Expectations • religious absences: contact me ASAP • students with disabilities: contact the DRS ASAP • jokes/comments about sex, gender, race, ethnicity, religion, etc. are inappropriate for class, emails, office hours, chats etc. • if someone is making you feel unwelcome/uncomfortable, please contact me or the TAs privately • if you are making someone feel unwelcome/uncomfortable the adult response is to accept responsibility and apologize • not to say "it was just a joke/meme" or "you're too sensitive" • have you considered being nice? • humans are rational and emotional. • consider others' happiness. • if you fail to acknowledge your own emotions, you are doomed to be controlled by them. CS447

7. Teaching philosophy • you are a student. you’re supposed to be confused. • I wanna help you understand! • No questions are dumb! • Never be afraid to ask them! • DON’T STRUGGLE IN SILENCE ON YOUR PROJECTS/LABS!!!!! • what is a university setting good for today? • focus, practice, and access to people who know stuff • in other words, me • it is my job to teach you, please let me do my job CS447

8. I can tell when you cheat :^) • first cheat, fail the assignment; second cheat, fail the class. • don't post your code on github • don't "help" your friends by giving them code CS447

9. That being said… • I trust you! • I try to be accommodating about extensions and such • I don’t think most cheaters are being lazy • but you’re an adult, and are responsible for your actions. • if you're confused, don't cheat, ask me for help. • again, that's what I'm here for?????????? • you can work with one partner on projects as long as… • you inform me ahead of time, • and you do not share code! CS447

10. Introduction and Context CS447

11. Goals of this course • ”447 tries to convince you that computers exist.” – Dr. Misurda • 447 and 449 teach some similar topics from different angles: • data representation • memory organization • how programs really run • the call stack and calling conventions • this course also establishes important fundamental skills: • numerical bases and representation • logical operations • understanding logic diagrams CS447

12. More goals • Java has poisoned your mind • ok it's fine for algorithms but it's too high level to explain computer • learning assembly is like a car mechanic learning how an engine runs CS447

13. Where does this material fit in with CS and EE? • the “hardware-software interface” • where CS and EE overlap • each layer affects/is affected by layers above and below • ISA: Instruction Set Architecture • Programmer's interface to the computer hardware • logic design • how we make rocks Do Stuff • doing Lots of Stuff (aka a CPU) more abstract more concrete CS447

14. Classes of computers: Embedded (Microcontrollers) • very cute • 8/16-bit architectures are still common • as little as 32 BYTES of memory! • almost always run one, built-in program • focus on ultra-low power, cost, and size • becoming more common every day • “Internet of Things” (IoT) • now your fridge can crash, your TV can crash, your dishwasher can crash, and your lightbulbs can be a botnet • what a stupid future CS447

15. Classes of computers: Consumer-grade (PC/Mobile) • 1-8 cores, 32/64-bit architectures, MB-GB of memory, GB-TB of persistent storage • multitaskingoperating systems • similar capabilities, different design goals • focus is real-time user interaction: productivity, media, browsing, games • despite what the book says, I really don’tthink we’re in a “Post-PC” era • who’s gonna do all their work on a touchscreen usinggimped sandboxed apps CS447

16. Classes of computers: Servers and Mainframes • from high end desktops to much more powerful machines or groups of machines • dozens of cores, 32GB+ of RAM, massive storage systems, very high-speed networking • focus on real-timedata delivery - either from storage or after processing • redundancy and hot-swappability • goal is 100% uptime • power and cooling become huge concerns CS447

17. Classes of computers: Supercomputers • cluster of hundreds to thousands of CPUs • focus on crunching ENORMOUS datasets non-interactively • science, research, design, and simulation • and now, stock trading and "cryptocurrencies"… CS447

18. General computer organization Memory Persistent Storage Control Registers Datapath Other Peripherals Other Computers Processor Input/OutputDevices Network CS447

19. Machine andAssembly Languages CS447

20. Lost in translation • "high-level" programming languages like Java exist for us intdoSomething() {this.x = 10; returnblarf();} 100010011111010000000000001000110111111100000?????? computers can only follow instructions written in machine language. compilers and VMs turn HLLs into machine language. CS447

21. What is machine language? • a computer has a fixed set of things it can do. • machine language is a numerical encoding of those operations. you could write "programs" by listing the columns/rows of buttons to press in order: (2,2)(4,4)(3,1)(3,4) 5 + 9 = but if we used that same "program" on a different calculator… (2,2)(4,4)(3,1)(3,4) CE * MS 6 CS447

22. What is assembly? • assembly is a human-readable representation of machine code • so it gives us direct control over the hardware… • …but at the expense of so many useful things the CPU is no more "intelligent" than a hand which can listen to instructions and push buttons on a 4-function calculator. CS447

23. Is assembly language useful today? • “assembly is fast, so we should use it for everything!”no, • it's not great for writing large programs • it can be dangerous, like with the Therac-25 • still useful for debugging (like in 449!) • if you write a compiler, you have to generate it • since that's what a compiler does • good for extremely performance critical low-level code, like: • device drivers • some parts of operating systems • High Performance Computing (simulations etc.) • increasingly fewer parts of video games • and… CS447

24. Embedded systems • you would be amazed how many CPUs are in any given device • many of these are programmed largely or entirely in assembly • many people use C but they're wrong, CS447