Hardware: The CPU & Storage

Chapter 5

How to Buy a Multimedia Computer

Key Questions5.1 What is a CPU? What are the three components of

a CPU and what are their functions?5.2 What are machine languages and how instructions

are executed?5.3 How is data represented in a computer; what are the

components of the system cabinet; what are processing speeds; how do the processor and memory work; and what are some important ports, buses, and cards?

5.4 What are the features of floppy disks, hard disks, optical disks, magnetic tape, smart cards, and online secondary storage?

CPU and Main Memory CPU: Central Processing Unit

– the “brain” of the computer– Control the operating of the

computer

Main Memory– Hold data being processed– Hold Program being executed– Primary Storage– RAM: Random Access Memory

The CPU and main memory

Main Memory Random Access Memory (RAM) Primary storage or memory Used to

– Holds data for processing– Holds instructions for processing data

Main memory is volatile:– the contents are lost when the power is

turned off.– Therefore, the data must be saved to a

secondary storage device for later use.

Main Memory - cont’d The more memory, the more powerful

– Hold more programs/data at a time. The capacity of memory varies with

different computers– bit or binary digit: 0/1– byte (8 bits each): one character– Kilobyte: 1024 bytes = 1 thousand– Megabyte: 1024 Kilobytes = 1 million– Gigabyte: 1024 Megabytes = 1 billion– Terabyte: 1024 Gigabytes = 1 trillion

Each byte has a unique address

Three Components of a CPU The control unit

– Like a symphony director– Control the rest of the system to carry out

program’s instructions. The Arithmetic/logic unit (ALU)

– Perform arithmetic and logical operations Registers:

– Fastest storage device– instruction register: hold the instruction to be

executed next– data registers: store data to be processed by ALU– address registers: Hold the addresses of RAM

System Clock and Word Size System clock

– Generate a sequence of digital pulses– To control how fast the processor executes– MHz: 1 million pulses per second– The faster the clock, the faster the processor.

Word Size– The # of bits the CPU can manipulate at a time.– A 32-bit-word PC is faster than an 8-bit-word PC

with the same system clock

The Power of a Processor – Determined by the system clock and word size.

Machine Language A Language a computer hardware can run

directly. Programs in BASIC or PASCAL must be

translated into the machine language before it is executed by the hardware.

An instruction consists of three parts– operation code: add/subtract– two operands: source and destination– Example: add M(10), M(20)

01011100 Add00001000 operand 100010100 operand 2, location of

result

How an Instruction is Processed Instructions are stored in memory

– The CPU can only execute instructions that are stored in memory, not on 2nd storage.

Machine Cycle: • a series of operations performed to execute a

single program instruction– Instruction cycle

• The control unit fetches the instruction from RAM to the instruction register

• It then decodes the instruction– Execution cycle

• The ALU executes the instruction• It then stores the result in memory

The machine cycle

How Data is Represented Binary System: Using Two States: bits Representation of numbers

– Position value• Decimal

– E.g., 342, it reads three hundred forty two,or three hundreds, four tens, and

two ones.I.e., each position has position valueSo, 3*102 + 4*101 + 2*100

• Binary– E.g., 10111

The position value of position i is ith power of 2Starting from the rightmost bit as position zero.So, 1*24 + 0*23 + 1*22 +1*21+1*20

= 16 + 0 + 4 + 2 + 1 = 23

How Data is Represented Binary System: Using Two States: bits Binary Coding Schemes for symbols/letters

– EBCDIC: • Extended Binary Coded Decimal Interchange code.• One byte for a character• Used on mainframe computers

– ASCII: • American Standard Code for Information Interchange• One byte for a character• Used on microcomputers

– Unicode: • Code foreign characters as well as English.• Two bytes for a character.• Used more and more

Binary data representation of symbols

Two coding schemes: EBCDIC and ASCII-8

The Microcomputer System Unit Power Supply

– Surge protectors• Prevent damages from power surges

– Uninterruptable power supply (UPS)• Provide temporary power supply when the main power is

off so the user can save data to disk. Motherboard

– The circuit that connects all the devices together. CPU Chip

– Intel-type chips– Motorola-type chips

• “68000”-series• PowerPC

System unit and motherboard components

Microcomputers and microprocessorsManufacturer and Chip Date

IntroducedSystemsChip

ClockSpeed (MHz)

BusWidth

Intel 8088 1979 IBM PC, XT 4-8 8Motorola 68000 1979 Macintosh Plus, SE:

Commodore Amiga8-16 16

Intel 80286 1981 IBM PC/AT, PS/2 Model 50/60;Compaq Deskpro 286

8-28 16

Motorola 68020 1984 Macintosh II 16-33 32Sun Microsystems RISC 1985 Sun Sparcstation 1, 300 20-25 32Intel 80386DX 1985 IBM PS/2; and compatibles 16-33 32Motorola 68030 1987 Macintosh IIx series, SE/30 16-50 32Intel 80486DX 1989 IBM PS/2; and compatibles 20-50 32Motorola 68040 1989 Macintosh Quadras 25-50 32IBM RISC 6000 1990 IBM RISC/6000 workstation 20-50 32Sun Microsystems 1992 Sun Sparcstation LX 50 32Intel Pentium 1993 Compaq Deskpro; IBM and

compatibles60-166 64

IBM/Motorola/Apple 1994 Power Macintoshes; Power 60-150 64PowerPC RISC Computing PowerWaveIntel Pentium Pro 1995 Compaq Proliant; Data General

server150-200 64

Intel Pentium MMX 1996 Dell; Gateway 2000 166-233 64Intel Pentium II 1997 Compaq Deskpro and

compatibles233-400 64

Apple PowerPC 1998 Power Macintoshes G3 233-266 64

The Microcomputer System Unit Specialized Processor Chips

– Math coprocessor chip– Graphics coprocessor chip– Types of processing

• Serial• Parallel

RAM Chips– Main memory or primary storage– Inline memory modules (SIMM / DIMM)

• Dynamic RAM (DRAM)• Static RAM (SRAM)

The Microcomputer System Unit

ROM Chips Other Forms of Memory

– Cache memory– Video memory or video RAM

Expansion Slots & Boards– Expanded memory– Display adapter or graphics adapter– Controller cards

The Microcomputer System Unit

Bus Lines– Expansion bus– Local bus

Ports– Parallel ports– Serial ports or RS-232 ports– Video adapter ports– Small computer system interface (SCSI)

Buses

I. Storage Fundamentals

Units of Measurement for Storage– Kilobyte/Megabyte/Gigabyte/Terabyte

Data Access Methods– Sequential Storage

• magnetic tapes

– Direct Access Storage• Hard disks, floppy disks, CD-ROMs

II.Criteria for Rating Storage Devices

Storage Capacity– # of bytes the disk can hold

Access Speed– the time needed to locate data

Transfer Rate– the speed at which data is transferred

Removability– the device that can be removed/installed

Cost– $$$

III. Diskettes

The Disk Drive1. Read2. Write

How A Disk Drive works– Magnetic coating on the disk– Read/Write head (R/W head)– While disk spins, R/W head can read/write

Cutaway view of a disk drive

Diskettes

C. Characteristics of Diskettes– Tracks and Sectors

• track: a circular band on the surface• Sector: a segment of track

– Unformatted versus formatted disks• Format: define tracks and sectors

– Data capacity—sides and densities– Write-protect features

Diskette anatomy

IV. Hard Disks

Hard-disks– “Multiple diskettes stacked in one pack.”– “Each diskettes has its own R/W on both sides”

Hard-disk Connections– SCSI: Small Computer System Interface – EIDE: Enhanced Integrated Drive Electronics

Fragmentation & Defragmentation– Cluster: the unit the computer can access

at a time from disk, multiple sectors – Fragmentation: a file spread out over many

noncontiguous sectors

Microcomputer hard-disk drive

Multiple disks and cylinders

V. Optical Disks 

CD-ROM (Compact Disk - Read Only Memory)– Data is read/written through laser beams– Single-speed: 1x = 150KB/Second, 150kbps

16x = 2400kbps, 32x = 4800kbps CD-R Disks: Recording Your Own CDs

– Compact disk—recordable– Compact disk - Recordable and reWriteable

DVD: The “Digital Convergence” Disk– New generation of high-density CD-ROM

Optical disks