Welcome to Computer Organization and Assembly! · 2020-04-07 · Classes of computers: Servers and Mainframes from high end desktops to much more powerful machines or groups of machines

Welcome!

CS/COE 0447

Luís Oliveira

Original slides by: Jarrett BillingsleyModified with bits from: Bruce Childers, David Wilkinson

Welcome!

● My name is Luis (pronounced Loo-eesh, but I don’t really care ☺ )

● I’m not from these parts as you can tell from my accent

o I come from Portugal

● course site: cs.pitt.edu/~loliveira orluisfnqoliveira.github.io/CS447o all the stuff I talk about today is on the course site

● email: loliveira@pitt.edu● office: 5421 SENSQ (check site)

● office Hours: TBD (check the site)

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i before e except after c…

and this guy’s name!

Textbook

● Computer Organization & Design

(Patterson & Hennessy)

● Not mandatory!

o Get it if you really want

o No readings, no exercises

o May reference it once in a while

● gets into a lot of detail

o fun read if you pick this stuff up easily

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Grading

● There will be no attendance

o But you should come to classes!

o Sometimes the slides alone may not be clear enough

▪ Even from seasoned professors! (I know, I’ve been there!)

● labs: 20%

o there'll be around 12? (~one a week)

o lowest 2 lab grades are dropped

● 3 projects: 40%

o two in MIPS assembly language, one in Logisim

o 15% two highest grades, 10% lowest grade

● 2 exams: 40%

o 1 midterms, 1 (semi-cumulative) final

o Lowest grade 15%; highest is 25%

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Expectations● Religious absences are excused: contact me ASAP

● Students with disabilities should contact the Office of Disability Resources and Services (DRS) if you haven’t alreadyo 216 William Pitt Union; 412-648-7890; TTY:412-383-7355

● Please, no comments about sex, gender, race, ethnicity, religion, etc..o Anywhere!o Just be nice!

● Cheating: Don’t!o 0 on assignment first time, o fail the course second time.o Do not publish your work in public palaces (no github!)o you can also talk about labs, but still no sharing stuff

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DO NOT CHEAT!

● If you're confused, don't cheat, ask me for help?

o Hot tips for not cheating:

1. Don’t!

2. Do not!

o You have LOTS of resources

▪ Me! and the TAs

▪ Undergraduate Helpdesk (CRC)

● People can tell when you cheat

o It is usually quite obvious!

o So don’t do it, it’s not worth it!

o The university is quite strict about it.

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Teaching

● No questions are dumb!

o NEVER BE AFRAID TO ASK THEM!

o DON’T STRUGGLE IN SILENCE ON YOUR PROJECTS/LABS!!!!!!!

● Yes, you can probably learn all this stuff on your own

o But in lectures you have access to me

o You can ask questions, and get the answers promptly!

o Please… be interactive ☺

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Introduction and Context

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Goals of this course● How does a CPU work?o Looking under the hoodo How are programs executed?o CS 449 looks at the programs

● Topics coveredo Data representationo Assembly languageo Program execution

● Learning important fundamental skills:o Representing numbers in different bases (binary, hexadecimal, …)o Logical operations (Boole?)o Understanding logic diagrams o Programming an assembly language

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Computational Theory

Algorithm Design

Applications

Operating Systems

ISA

Logic Design

Electrical Design

Physics

mo

re a

bstra

ct mo

re co

ncre

teWhere 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

o Programmer's interface to the

computer hardware

● logic design

o how we make 0’s and 1’s do stuff

o Rocks doing Lots of Stuff (aka a CPU)

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More goals

● Let’s learn Assembly!

● Let’s unlearn High-level languages (Java, C)

o Datatypes/structures? Nope!

o Infinite number of variables? Nope!

● “Learning assembly is like a car mechanic learning how an engine

runs”

o Normal people don’t want to, but it’s fun to take things apart!!!

▪ Also putting them back together and (hopefully) see them work!

o And we are not normal people!

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Computers

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The pre-history of computers

● Charles Babbage (1792-1871) designed the analytical engine

o It already included the essential ideas of modern computers

▪ Inputs and outputs

▪ Execution of operations

▪ Automatic control of operation

o However, due to its complexity (lack of funding) it was never built

● From that point onwards many other advances were made

o George Boole developed Boolean Algebra

o The Hollerith Machine – Electro-mechanical machine used to

process census data in the US (reading perforated cards)

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The pre-history of computers

● Leading to the first use of relays (electrical switches) in the 1930-40’s

o George Stibitz (Bell Labs)

▪ Model K – binary addition with relays (Boolean algebra)

▪ Complex Number Computer – used remotely via telegraph lines

▪ Art with Amiga (1990s) - http://stibitz.denison.edu/art.html

o Konrad Zuse (Germany)

▪ World's first programmable computer

▪ Several relay-based computers

– Used for military calculations

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The first “modern” computers

● 1946 – ENIAC (Electronic Numerical Integrator and Computer),

University of Pennsylvania

o Developed during WWII to calculate balistic missile trajectories

▪ 18000 valves (tubes)

▪ 1500 relays

▪ 30 tons

▪ 175 kW

▪ 5000 additions / s

▪ 357 multiplications / s

▪ 40 divisions / s

▪ Programs "hardwired"

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U. S. Army Photo

The first “modern” computers

● 1947 – EDVAC (Electronic Discrete Variable Automatic Computer),

University of Pennsylvania

o The ENIAC team (joined by John Von Neumann) created a

computer with a new concept:

▪ "Memory Stored Program" – same as data

o Became operational in 1951

● 1949 – EDSAC (Electronic Delay Storage Automatic Calculator),

Cambridge University, Maurice Wilkes

o Based on the first EDVAC draft

16https://en.wikipedia.org/wiki/EDSAC

The first “modern” computers

● 1951 – UNIVAC

o First commercial computer!

▪ Sold 46! Units

▪ Used to predict the 1952 presidential election

o Bi-quinary

o Used a MERCURY!! memory module (as did the EDSAC)

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https://en.wikipedia.org/wiki/Delay_line_memory

Delay

Storage

The transistor and integrated circuits● 1971 – Intel 4004o 4-bit microprocessoro with 2300! Transistors

● 1993 – MIPS R4000o RISC 32-bito 1.3 Million transistors

● 2004 – Pentium 4o x86 32-bit o 125 Million transistors

● 2017 – Kaby Lakeo x86_64 64-bito >1000 Million! (undisclosed?)

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Moore’s Law

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82944 processors

from a supercomputer

Where used to simulate

1s of human brain activity

In 40m

Illustration:

https://www.wired.com/2013/05/neurologi

st-markam-human-brain/

All different but all

(mostly) the same

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Classes of computers: Embedded (Microcontrollers)

● 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)

o now your fridge can crash, your TV can crash,

your dishwasher can crash, everything can crash!

o Even your lightbulbs

can be hacked!

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Classes of computers: Consumer-grade (PC/Mobile)

● 1-8 cores, 32/64-bit architectures, MB-GB of

memory, GB-TB of persistent storage

● multitasking operating systems

● similar capabilities, different design goals

● focus is real-time user interaction:

productivity, media, browsing, games

● Energy consumption is still relevant

o Mobile

● But, are we in a post-PC world?

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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-time data delivery - either from

storage or after processing

● redundancy and hot-swappability

● goal is 100% uptime

● power and cooling become huge concerns

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Classes of computers: Supercomputers

● cluster of hundreds to thousands of CPUs

● focus on crunching ENORMOUS datasets non-interactively

● science, research, design, and simulation

o and now, stock trading and "cryptocurrencies"…

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General computer organization

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Control

Registers

Datapath

Processor

Memory

Persistent

Storage

Other

Peripherals

Other

Computers

Input/Output

Devices

Network

Assembly

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So what exactly is assembly?

● Assembly: Human-readable representation of machine code

● Machine code: Machine code is what a CPU actually runs

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00000001000000000010000000100000

add a0, t0, zero

So what exactly is assembly?

● Assembly: Human-readable representation of machine code

● Machine code: Machine code is what a CPU actually runs

● Essentially it's the "atoms" that make up a program

o CPUs are actually pretty simple in concept

▪ (oh wait, we still have a whole semester about it… huh)

● Each CPU has its own machine language and therefore its own

assembly language

● We’ll be using MIPS:

o Not that common

o Yet, often found in surprising places. (Nintendo 64, PS1/2, FPGAs)

o Very influential, and most common assembly looks like it.

▪ ARM and RISC-V are similar-ish ISA seeing much more usage

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is assembly language useful today?

● Short answer: YES

● Assembly is “fast”, so we should use it for everything!

--- NO!!! ---

● No type-checking, no control structures, very few abstractions

o Probably you can be fairly fast using compiler optimizations

--- Fairly impractical for large things ---

● Tied to a particular CPU.

o So, large programs have to be rewritten (usually) to work on new

things.

● Yet: good for specialized stuff.

o Critical paths and “boot” code in Kernels / Operating Systems

o HPC (simulators, supercomputer stuff)

o Real-time programs (video games; tho increasingly less / abstracted away)

o And…

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Embedded systems

● You’d be amazed at how many consumer devices have CPUs.

● Many are programmed largely/entirely in assembly (or C)

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So where does assembly fit?

● Programs written in C, etc are generally translated into assembly.

o And then into machine code.

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int main(void)

{

printf(“Hello world\n”);

return 0;

}

hello.c

.data

str: .asciiz “Hello world\n”

.text

.globl main

main:

li v0, 4

la a0, str

syscall

j ra

hello.s

Compile → by a compiler

Assemble → by an assembler

10010001001010001010100…

hello.o

Libraries

00101001010100101001001…

crt0.o

hello.exeLink

is assembly language useful today?

● Programs written in C, etc are generally translated into assembly.

o And then into machine code.

● Or you can look at the machine code of programs and get an

assembly code listing.

o And step through the program one instruction at a time.

● When programs crash (sometimes programs you don’t have the code

for) you can look at the assembly code and assess.

● Programs exist to help you (gdb, IDA Pro, radare, etc)

● In CS 449 you will apply this knowledge (using gdb).

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and next time we'll start

● Data representations

● How does a CPU look at numbers, letters, etc.

● Learn about number bases:

o Decimal (that’s what we use!)

o Binary

o Octal

o Hexadecimal

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