Computer Organization CS224 Fall 2012 “Welcome to our course” Will Sawyer & Fazlı Can With...

Computer OrganizationCS224

Fall 2012

“Welcome to our course”Will Sawyer & Fazlı Can

With thanks to M.J. Irwin, D. Patterson, and J. Hennessy for some lecture slide contents

CS224 Course Contents

Overview of computer technologies, instruction set architecture (ISA), ISA design considerations, RISC vs. CISC, assembly and machine language, translation and program start-up.

Computer arithmetic, arithmetic logic unit, floating-point numbers and their arithmetic implementations.

Processor design, data path and control implementation, pipelining, hazards, pipelined processor design, hazard detection and forwarding, branch prediction and exception handling.

Memory hierarchy, principles, structure, and performance of caches, virtual memory, segmentation and paging.

I/O devices, I/O performance, interfacing I/O.

Intro to multiprocessors, multicores, and cluster computing.

CS224 Spring 2012

CS224 Policies

Everything is on the Web site:

found @ CS Dept > Course Home Pages > CS224http://www.cs.bilkent.edu.tr/~will/courses/CS224/

Numerical average will be calculated from:• 6 Problem Sets 10%• 2 Projects 30%• Midterm 25%• Final exam 35%

TO PASS, you must:• have exam average > 40% (weighted average)• not drop out (FX) : attend class sometimes, do projects & exams• have overall course performance that is passing

CS224 Spring 2009 Computer Organization & Design by Patterson & Hennessy

Why learn this stuff?

• You want to call yourself a “computer engineer”

• You want to build software people use (need performance)

• You need to make a purchasing decision or offer “expert” advice

• Both Hardware and Software affect performance:

– Algorithm determines number of source-level statements

– Language/Compiler/Architecture determine machine instructions(Chapter 2 and 3)

– Processor/Memory determine how fast instructions are executed(Chapter 4 and 5)

– I/O and Number_of_Cores determine overall system performance

(Chapter 6 and 7)

CS224 Spring 2012

Organization of a Computer

• Five classic components of a computer – input, output, memory, datapath, and control

datapath + control = processor (CPU)

CS224 Spring 2012

AMD’s Barcelona Multicore Chip

http://www.techwarelabs.com/reviews/processors/barcelona/

Core 1 Core 2

Core 3 Core 4

Northbridge

512K

B L

2

512K

B L

2 51

2KB

L2

512K

B L

2

2MB

sh

ared

L3

Cac

he

Four out-of-order cores on one chip

1.9 GHz clock rate

65nm technology

Three levels of caches (L1, L2, L3) on chip

Integrated Northbridge


Function Units in a Computer


Magnetic Storage

Source: Quantum Corp

Disk capacity increasing 60%/year for common form factor

CS224 Spring 2012

Classes of Computers

• Desktop computers: Designed to deliver good performance to a single user at low cost usually executing 3rd party software, usually incorporating a graphics display, a keyboard, and a mouse

• Servers: Used to run larger programs for multiple, simultaneous users typically accessed only via a network and that places a greater emphasis on dependability and (often) security

• Supercomputers: A high performance, high cost class of servers with hundreds to thousands of processors, terabytes of memory and petabytes of storage that are used for high-end scientific and engineering applications

• Embedded computers (processors): A computer inside another device used for running one predetermined application. Very often cost, power, and failure rate are more important than performance.

CS224 Spring 2012

Growth in Embedded Processor Sales(embedded growth >> desktop growth !!!)

Where else are embedded processors found?

Courtesy, Intel ®

Dual Core Itanium with

1.7B transistors

Moore’s Law

feature size&

die size

In 1965, Intel’s Gordon Moore predicted that the number of transistors that can be integrated on single chip would double about every two years


Moore’s Law for CPUs and DRAMs

Technology Scaling Road Map

Year 2004 2006 2008 2010 2012

Feature size (nm) 90 65 45 32 22

Intg. Capacity (BT) 2 4 6 16 32

• Fun facts about 22nm transistors– 120 million can fit on the head of a pin– You could fit more than 4,000 across the width of a human

hair– If car prices had fallen at the same rate as the price of a

single transistor has since 1968, a new car today would cost less than 1 cent


Semiconductors

• 50 year old industry– Still has continuous improvements, in each generation– New generation every 2-3 years

• 30% reduction in dimension 50% in area• 30% reduction in delay 50% speed increase• Current generation: Reduce cost and increases performance

– Processors are fabricated on ingots cut into wafers which are then etched to create transistors

– Wafers are then diced to form chips, some of which have defects

– Yield is the measurement of the good chips• Next generation: Larger with more functions


Main driver: device scaling ...

.

CS224 Spring 2012

Semiconductor Manufacturing Process for Silicon ICs

What Happened to Clock Rates?

Clock rates hit a “power wall”

CS224 Spring 2012

Processor performance growth flattens!

CS224 Spring 2012

The Latest Revolution: Multicores• The power challenge has forced a change in the design of

microprocessors– Since 2002 the rate of improvement in the response time of

programs on desktop computers has slowed from a factor of 1.5 per year to less than a factor of 1.2 per year

• Since 2006, all desktop and server companies are shipping microprocessors with multiple processors – cores – per chip

Product AMD Barcelona

Intel Nehalem

IBM Power 6 Sun Niagara 2

Cores per chip 4 4 2 8

Clock rate 2.5 GHz ~2.5 GHz? 4.7 GHz 1.4 GHz

Power 120 W ~100 W? ~100 W? 94 W

The plan is to double the number of cores per chip per generation (about every two years)

Power as a Performance Metric• Power consumption – especially in the embedded market where

battery life is important– For power-limited applications, the most important metric is

energy efficiency


Computer Architecture

ComputerArchitecture

I/O systemInstr. Set Proc.

Compiler

OperatingSystem

Application

Logic Design

Circuit Design

Instruction Set Architecture

Firmware

Implementation

Layout


The Instruction Set: a Critical Interface

instruction set

software

hardware



• A very important abstraction

– interface between hardware and low-level software

– standardizes instructions, machine language bit patterns, etc.

– advantage: different implementations (cost, performance,

power) of the same architecture

– disadvantage: sometimes prevents using new innovations

• Common instruction set architectures:– IA-32, PowerPC, MIPS, SPARC, ARM, and others



• ISA, or simply architecture – the abstract interface between the hardware and the lowest level software that encompasses all the information necessary to write a machine language program, including instructions, registers, memory access, I/O, …

• ISA Includes– Organization of storage– Data types– Encoding and representing instructions– Instruction Set (or opcodes)– Modes of addressing data items/instructions– Program visible exception handling

• Specifies requirements for binary compatibility across implementations (ABI)


Case Study: MIPS ISA

• Instruction Categories– Load/Store– Computational– Jump and Branch– Floating Point– Memory Management– Special

R0 - R31

PCHI

LO

OP

OP

OP

rs rt rd sa funct

rs rt immediate

jump target

3 Instruction Formats, 32 bits wide


Execution Cycle

Instruction

Fetch

Instruction

Decode

Operand

Fetch

Execute

Result

Store

Next

Instruction

Obtain instruction from program storage

Determine required actions and instruction size

Locate and obtain operand data

Compute result value or status

Deposit results in storage for later use

Determine successor instruction


Levels of Representation

High Level Language Program

Assembly Language Program

Machine Language Program

Control Signal Specification

Compiler

Assembler

Machine Interpretation

temp = v[k];

v[k] = v[k+1];

v[k+1] = temp;

lw $15, 0($2)lw $16, 4($2)sw $16, 0($2)sw $15, 4($2)

0000 1001 1100 0110 1010 1111 0101 10001010 1111 0101 1000 0000 1001 1100 0110 1100 0110 1010 1111 0101 1000 0000 1001 0101 1000 0000 1001 1100 0110 1010 1111

°°

ALUOP[0:3] <= InstReg[9:11] & MASK [i.e.high/low on control lines]

CS224 Spring 2012

Advantages of HLLs• Higher-level languages (HLLs)

• Compilers convert source code to object code• Libraries simplify common tasks

Allow the programmer to think in a more natural language and for their intended use (Fortran for scientific computation, Cobol for business programming, Lisp for symbol manipulation, Java for web programming, …)

Improve programmer productivity – more understandable code that is easier to debug and validate

Improve program maintainability Allow programs to be independent of the computer on which

they are developed (compilers and assemblers can translate high-level language programs to the binary instructions of any machine)

Emergence of optimizing compilers that produce very efficient assembly code optimized for the target machine

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