Hardware: The CPU & Storage Chapter 5 How to Buy a Multimedia Computer

Key Questions 5.1 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 n CPU: Central Processing Unit –the “brain” of the computer –Control the operating of the computer n Main Memory –Hold data being processed –Hold Program being executed –Primary Storage –RAM: Random Access Memory

The CPU and main memory

Main Memory n Random Access Memory (RAM) n Primary storage or memory n Used to –Holds data for processing –Holds instructions for processing data n 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 n The more memory, the more powerful –Hold more programs/data at a time. n 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 n Each byte has a unique address

Three Components of a CPU n The control unit –Like a symphony director –Control the rest of the system to carry out program’s instructions. n The Arithmetic/logic unit (ALU) –Perform arithmetic and logical operations n 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 n 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. n 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 n The Power of a Processor –Determined by the system clock and word size.

Machine Language n A Language a computer hardware can run directly. n Programs in BASIC or PASCAL must be translated into the machine language before it is executed by the hardware. n An instruction consists of three parts –operation code: add/subtract –two operands: source and destination –Example: add M(10), M(20) Add operand operand 2, location of result

How an Instruction is Processed n Instructions are stored in memory –The CPU can only execute instructions that are stored in memory, not on 2nd storage. n 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 n Binary System: Using Two States: bits n 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 value So, 3* * *10 0 Binary –E.g., The position value of position i is i th power of 2 Starting from the rightmost bit as position zero. So, 1* * *2 2 +1*2 1+ 1*2 0 = = 23

How Data is Represented n Binary System: Using Two States: bits n 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 n 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. n Motherboard –The circuit that connects all the devices together. n CPU Chip –Intel-type chips –Motorola-type chips “68000”-series PowerPC

System unit and motherboard components

Microcomputers and microprocessors

The Microcomputer System Unit n Specialized Processor Chips –Math coprocessor chip –Graphics coprocessor chip –Types of processing Serial Parallel n RAM Chips –Main memory or primary storage –Inline memory modules (SIMM / DIMM) Dynamic RAM (DRAM) Static RAM (SRAM)

The Microcomputer System Unit n ROM Chips n Other Forms of Memory –Cache memory –Video memory or video RAM n Expansion Slots & Boards –Expanded memory –Display adapter or graphics adapter –Controller cards

The Microcomputer System Unit n Bus Lines –Expansion bus –Local bus n Ports –Parallel ports –Serial ports or RS-232 ports –Video adapter ports –Small computer system interface (SCSI)

Buses

I. Storage Fundamentals n Units of Measurement for Storage –Kilobyte/Megabyte/Gigabyte/Terabyte n Data Access Methods –Sequential Storage magnetic tapes –Direct Access Storage Hard disks, floppy disks, CD-ROMs

II.Criteria for Rating Storage Devices n Storage Capacity –# of bytes the disk can hold n Access Speed –the time needed to locate data n Transfer Rate –the speed at which data is transferred n Removability –the device that can be removed/installed n Cost –$$$

III.Diskettes n The Disk Drive 1.Read 2.Write n 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 n 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 n Hard-disks –“Multiple diskettes stacked in one pack.” –“Each diskettes has its own R/W on both sides” n Hard-disk Connections –SCSI: Small Computer System Interface –EIDE: Enhanced Integrated Drive Electronics n 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 n CD-ROM (Compact Disk - Read Only Memory) –Data is read/written through laser beams –Single-speed: 1x = 150KB/Second, 150kbps 16x = 2400kbps, 32x = 4800kbps n CD-R Disks: Recording Your Own CDs –Compact disk—recordable –Compact disk - Recordable and reWriteable n DVD: The “Digital Convergence” Disk –New generation of high-density CD-ROM

Optical disks