Chapter 5 Computing Components

The (META) BIG IDEA Cool, idea but maybe too big DATA – Must be stored somewhere in a storage device PROCESSING – Data must be moved around and manipulated 5-2

Chapter Goals Components of a von Neumann machine Von Neumann fetch-decode-execute cycle – What does “running a program” mean, anyway? Limitations of von Neumann architecture 5-3

Chapter Goals Memory “Pyramid” – Memory has characteristics and trandoffs – Primary vs Secondary memory Primary memory organization (RAM) Secondary memory (auxiliary storage devices) Alternatives to von Neumann architecture 5-4

Computer Components 5-5

Motherboard 5-6

WHAT A MESS!!! We need to ABSTRACT 5-7

We need Some Abstraction!!! Real hardware is messy Especially Intel architecture because of backward compatibility (aka legacy issues) We need some simpler models (abstractions) of von Neumann architecture Who has been to Disneyland?

Von Nuemann Architecture The parts are connected to one another by a collection of wires called a bus 5-9 Figure 5.2 Data flow through a von Neumann architecture

Von Nuemann Architecture The bus is SHARED by several devices This affects how data flows ANALOGY: – Who do you call most on your cell phone? – Some devices communicate more than others 5-10

von Neumann Architecture 5-11 Figure 5.1 The von Neumann architecture

Main Memory (RAM) 5-12

RAM Memory is a collection of cells, each with a unique physical address How many data bits? How many address bits? Page

What is in a CPU?? 5-14

CPU CPU Components Arithmetic Logic Unit Control Unit Registers 5-15 ALU (does the work) REG (holds data) CU (The Boss) MEMORY program

Arithmetic/Logic Unit Performs basic arithmetic operations: – Adding – Multiplying – Dividing Performs logical operations such as AND, OR, and NOT – Example: RGB color mixing 5-16

Registers Contain the data that the CPU is processing “at the moment” There is a set of registers 5-17

Control Unit Control unit controls the instruction cycle Reads in a SW program, one instruction at a time Tells the ALU what to do 5-18

Control Unit There are two special registers in the control unit – The instruction register (IR) contains the instruction that is being executed – The program counter (PC) contains the address of the next instruction to be executed 5-19

The Fetch-Execute Cycle The Control Unit makes the CPU go through the following cycle: 1)Fetch the next instruction 2)Decode the instruction 3)Execute the instruction – the cycle repeats – forever ! 5-20

Fetch-Decode-Execute Cycle 5-21

Memory Mixes 5-22 Computers contain a mix of different kinds of memory Why???? Will it always be this way?

Memory and the Memory Pyramid 5-23 CapacityCost & Speed Tape Magnetic Disk Cache Main RAM Flash RAM

Primary and Secondary Storage Primary Storage – aka “Main Memory” (usually RAM) – the “working memory” of the CPU – Fast – High $ per byte Secondary Storage – where all the stuff that is not being worked on “now” is stored (usually DISK) – Slow – Low $ per byte 5-24

Primary Memory - RAM RAM stands for Random Access Memory – Any location can be accessed quickly, – Same amount of time to access any location (aka ‘random’) RAM is volatile – Data is LOST when the power is turned off Primary (Main) memory is – Volatile – Limited – Expensive 5-25

Primary vs Secondary Computers have a BALANCE of Primary and Secondary Memory Trade offs: – Speed – Size – Cost 5-26

Secondary Memory Secondary memory is – Big – Cheap – Slower than Primary Memory Examples: – Magnetic Disk – CD Rom – Flash (Solid State Drives) 5-27

Magnetic Tape The first truly mass auxiliary storage device was the magnetic tape drive Cassette Tapes are still used for large data backups Figure 5.4 A magnetic tape5-17

Magnetic Disks A read/write head travels across a spinning magnetic disk, retrieving or recording data Figure 5.5 The organization of a magnetic disk 5-18

Compact Disks A CD drive uses a laser to read information stored optically on a plastic disk CD-ROM is Read-Only Memory – Approximately 700MB DVD stands for Digital Video Disk – Approximately 4 GB 5-30

QUESTION TIME Does the PERFECT MEMORY EXIST?? What would be its characteristics?? 5-31 Does anybody have a Solid State Drive (SSD) ??

Von BOTTLENECK Von Neumann has a fundamental limitation: The SHARED BUS!! 5-32

Alternatives to von Neumann Several alternative architectures exist Some are used to enhance von Neumann Examples: – Synchronous Processing (Parallel) – Pipelining (Serial) 5-33

Synchronous processing One approach to parallelism is to have multiple processors apply the same program to multiple data sets 5-34 Figure 5.7 Processors in a synchronous computing environment

Some Parallel Architecture Examples Google – Many servers in one building (“Server Farm”) SETI – Geographically Distributed Processors Quad Core and Tilera – Several CPUs on one chip 5-35

Pipelining Arranges processors in tandem, where each processor contributes one part to an overall computation 5-36 Figure 5.8 Processors in a pipeline

Pipelining Examples Like a manufacturing assembly line (cars) Some series of tasks can be pipelined – Example: game video processing 1.Build vector model 2.Wrap vectors in bitmaps 3.Generate camera view 5-37