Chapter 4 The Components of the System Unit

Instruction Data Information Instructions Data Information Ch 4 System Unit Ch 1 – Introduction Ch 2 – Internet & WWW Ch 3 – Application Software Ch 8 – System Software Ports Cards Buses Clock Power Drives Control Unit Arithmetic Logic Unit (ALU) Instruction Data Information Memory Input Devices Ch 5 Output Devices Ch 6 Information Data Instructions Data Information Storage Devices Ch 7

What is the system unit? Case that contains electronic components of the computer used to process data

What is the motherboard? Main circuit board of the system unit Also called system board

Components inside the system unit? Processor Memory Clock Adapter (extension) cards Sound card Video card Drive bays Power supply Ports Buses

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

Control unit is the component of the processor that directs and coordinates most of the operations in the computer Arithmetic logic unit (ALU) performs arithmetic, comparison, and other operations

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

Memory Processor Step 1. Fetch Obtain program instruction from memory Control Unit Memory Step 1. Fetch Obtain program instruction from memory Step 4. Store Write result to memory Step 2. Decode Translate instruction into commands ALU Step 3. Execute Carry out command

The processor contains registers, that hold data and instructions The processor contains circuits that perform instructions using data

The system clock controls the timing of all computer operations

System Clock Generates regular electronic pulses, or ticks, that set operating pace of components of system unit

How speed of the processor is measured? Each tick is a clock cycle Pace of system clock is clock speed Clock speeds are in the gigahertz (GHz- billion ticks per sec) Processor speed is also measured in millions of instructions per second (MIPS)

Instructions per 1 watt energy (in millions) (MIPW) Clock speed (GHz) Instructions per sec (MIPS) Instructions per 1 watt energy (in millions) (MIPW)

What is pipelining? CPU begins executing the second instruction before completing the first instruction Machine Cycle (without pipelining) Machine Cycle (with pipelining) Instruction 1 Instruction 2 Instruction 3 Instruction 4

Doing Laundry Ann, Brian, Cathy, Dave each have one load of clothes to wash, dry, fold, slash A B C D Washer takes 30 minutes Dryer takes 30 minutes Folder takes 30 minutes Stasher takes 30 minutes

Sequential Laundry Sequential laundry takes 8 hours for 4 loads 30 Time 6 PM 7 8 9 10 11 12 1 2 AM T a s k O r d e B C D A Sequential laundry takes 8 hours for 4 loads

Pipelined laundry takes 3.5 hours for 4 loads 12 2 AM 6 PM 7 8 9 10 11 1 Time 30 T a s k O r d e B C D A Pipelined laundry takes 3.5 hours for 4 loads

What is parallel processing? Using multiple processors simultaneously to execute a program faster Requires special software to divide problem and bring results together Control Processor Processor 1 Memory Processor 2 Memory Processor 3 Memory Processor 4 Memory Results combined

Single-core processor Multi-core processor One processor on a chip More then one processor on a chip

Data of various nature are presented inside a computer in a digital form. We will see how.

Analog signals are continuous and vary in strength and quality Digital signals are in one of two states: on or off

What is a bit?

Eight bits grouped together as a unit are called a byte. Each byte has a unique address. Each of eight bits in a byte has a position

What a byte contains vs. what an output device will convey? Contains: A sequence of 8 binary digits Means: Number Character Instruction Sound pitch Color … Depending on device

Representing numbers Numbers have the most natural presentation. Each bit of a byte has a value depending on the position of the bit in a byte. For example byte 01010101 carries numeric value of 64+16+4+1 = 85

Coding systems to represent text data ASCII—American Standard Code for Information Interchange Unicode—coding scheme capable of representing all world’s languages

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 What has to be stored? The operating system and other system software Application programs Data being processed and the resulting information

Memory consists of locations (bytes) Memory consists of locations (bytes). Each location in memory has an address The number of locations in memory is memory size. It is measured in kilobytes (KB or K), megabytes (MB), gigabytes (GB), or terabytes (TB)

Nonvolatile memory Volatile memory The system unit contains two types of memory: Volatile memory Loses its contents when power is turned off Example: RAM Nonvolatile memory Does not lose contents when power is removed Examples: ROM, flash memory

Read-only memory (ROM) refers to memory chips storing permanent data and instructions

Adapter (Extension) Cards A flash memory card allows users to transfer data from mobile devices to desktop computers An PC card adds various capabilities to computers

Flash memory can be electronically rewritten

Flash memory includes: Memory cards, USB flash drives, and PC Cards modules

Memory cache speeds the processes of the computer because it is faster than memory and stores repeatedly used information

Access time is the amount of time it takes the processor to read from memory. Measured in nanoseconds

Expansion slot Adapter card holds an adapter card enhances functions and provides connections to peripherals

With Plug and Play, the computer automatically configures adapter cards and peripherals as you install them

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

Port connects external devices to system unit

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

What are USB ports? USB (universal serial bus) port can connect up to 127 different peripherals together with a single connector type PCs typically have several USB ports Single USB port can be used to attach multiple peripherals Third USB device connects to second USB, and so on Second USB device connects to first USB First USB device connects to USB port USB 2.0

You can attach multiple peripherals using a single USB port with a USB hub

Firewire port SCSI port eSATA port IrDA port Serial port MIDI port Other types of ports include: Firewire port Bluetooth port SCSI port eSATA port IrDA port Serial port MIDI port

What are special-purpose ports? Allow users to attach specialized peripherals or transmit data to wireless devices MIDI (Musical Instrument Digital Interface) port IrDA (Infrared Data Association) port Bluetooth port

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

What is a serial port? Transmits one bit of data at a time Connects slow-speed devices, such as mouse, keyboard, modem

What is a parallel port? Connects devices that can transfer more than one bit at a time, such as a printer

Buses What is a bus? Channel that allows devices inside computer to communicate with each other Bus width determines number of bits transmitted at one time

Bays What is a bay? Opening inside system unit used to install additional equipment Drive bays typically hold disk drives

Power Supply and cooling Converts AC Power into DC Power Fan keeps system unit components cool

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