discovering computers 2012: chapter 4 1. the system unit the system unit is a case that contains...

Discovering Computers 2012: Chapter 4 1


The System Unit

• The system unit is a case that contains electronic components of the computer used to process data

10 Figure 4-1


The System Unit

• The inside of the system unit on a desktop personal computer includes:

Page 211 Figure 4-2

Drive bay(s)

Power supply

Sound card

Video card

Processor

Memory


The System Unit

• The motherboard is the main circuit board of the system unit– A computer chip contains integrated circuits

Page 212 Figure 4-3


Processor

• The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer– Contain a control unit and an arithmetic logic unit

(ALU)

Page 213


Processor

Page 213 Figure 4-4


Processor

• The control unit is the component of the processor that directs and coordinates most of the operations in the computer

• The arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations

Page 214


Processor

• For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle

Page 215 Figure 4-5


Processor

The processor contains registers, that temporarily hold data and instructions

The system clock controls the timing of all computer operations• The pace of the system clock is called the clock

speed, and is measured in gigahertz (GHz)Page 216


Processor

• A processor chip generates heat that could cause the chip to burn up

• Require additional cooling– Heat sinks– Liquid cooling

technology

Pages 219 - 220 Figures 4-9 – 4-10

Memory

• Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions, and the results of processing the data

• Stores three basic categories of items:

Discovering Computers 2012: Chapter 4 11Page 223

The operating system and other system software

Application programs

Data being processed and the

resulting information


Memory

• Each location in memory has an address• Memory size is measured in kilobytes (KB or K),

megabytes (MB), gigabytes (GB), or terabytes (TB)

Page 223 Figure 4-17


Memory

• The system unit contains two types of memory:

Pages 223 - 224

Volatile memory

Loses its contents when power is turned off

Example includes RAM

Nonvolatile memory

Does not lose contents when power is removed

Examples include ROM, flash memory, and

CMOS


Memory


15

• Memory Devices–Memory: Is one or more sets of chips

that store data/program instructions, either temporarily or permanently .

– It is critical processing component in any computer

–PCs use several different types

2. RAM,ROM,PROM,EPROM

16

RAM,ROM,PROM,EPROM

• Memory Devices–Two most important are

• RAM(Random Access Memory)• ROM(Read-only Memory)

–They work in different ways and perform distinct functions

–CPU Registers–Cache Memory

17

RAM• RAM is packaged as a chip.• Basic storage unit is a cell (one bit per cell).• Multiple RAM chips form a memory.• Random Access Memory

VolatileUsed for temporary storageTypical ranges 256 MB - 4 GB

• Random Access means direct access to any part of memory

18

Nonvolatile Memories(ROM)• DRAM and SRAM are volatile memories– Lose information if powered off.

• Nonvolatile memories retain value even if powered off.–Generic name is read-only memory (ROM).–Misleading because some ROMs can be

read and modified.

19

Nonvolatile Memories(ROM)• Types of ROMs– Programmable ROM (PROM)– Eraseable programmable ROM (EPROM)– Electrically eraseable PROM (EEPROM)– Flash memory (used in portable digital devices)

• Firmware (Program instruction used frequently)– Program stored in a ROM• Boot time code, BIOS (basic input/output

system)• graphics cards, disk controllers.


Memory

• Three basic types of RAM chips exist:


Dynamic RAM (DRAM) Static RAM (SRAM) Magnetoresistive

RAM (MRAM)


Memory

• RAM chips usually reside on a memory module and are inserted into memory slots



Memory

• The amount of RAM necessary in a computer often depends on the types of software you plan to use

6 Figure 4-21


Memory

• Memory cache speeds the processes of the computer because it stores frequently used instructions and data



Memory

• Flash memory can be erased electronically and rewritten– CMOS technology provides high speeds and consumes

little power

Pages 228 – 229Figure 4-23


Expansion Slots and Adapter Cards

• An expansion slot is a socket on the motherboard that can hold an adapter card

• An adapter card enhances functions of a component of the system unit and/or provides connections to peripherals– Sound card and video card



Expansion Slots and Adapter Cards

• Removable flash memory includes:– Memory cards, USB flash drives, and PC

Cards/ExpressCard modules



Ports and Connectors

A port is the point at which a peripheral attaches to or communicates with a system unit (sometimes referred to as a jack)

A connector joins a cable to a port

Page 232



• On a notebook computer, the ports are on the back, front, and/or sides

Pages 232 - 233 Figure 4-30



• A USB port can connect up to 127 different peripherals together with a single connector– You can attach multiple peripherals using a single USB

port with a USB hub




A Bluetooth wireless port adapter converts a USB port into a Bluetooth port

A smart phone might communicate with a notebook computer using an IrDA port

Page 235 Figures 4-33 – 4-34



• A port replicator is an external device that provides connections to peripherals through ports built into the device

• A docking station is an external device that attaches to a mobile computer or device


discovering computers 2012: chapter 4 1. the system unit the system unit is a case that contains...

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