PCH Module 1

B-Tech Lecture Notes Personal Computer Hardware

PCH-Module 1 http://btech-lecturenotes.blogspot.in/

Module 1: Introduction to Personal Computer

Hardware Components:

The following are the basic hardware components of a personal computer. They

are categorized according to their functions and use. Following components are most

commonly used pc hardware components and most commonly available components in

the market.

PC Hardware Components

1. Peripherals

a. Input/Output Devices

• Mouse

• Keyboard

• Touch Screen

• Joy Stick

• Monitor (CRT, LCD)

• Printers (Dot Matrix, Ink Jet, Laser Printer)

• Plotter

• Speakers

b. Disk Drives

• Floppy Disk

• Hard Disk

• CD – Compact Disc

• DVD – Digital Versatile Disc

• Blue Ray

• ZIP

c. SMPS – Switch Mode Power Supply

2. Logics

a. Mother Board

• Processor

• Processor Slot



o Slot Type

o Socket Type – Zero Insertion Force Socket

• Chip Set

o Clock Generator

o DMA Controller

• Co – Processor (currently built – in with main processor)

• Slots for Add – on – Cards (Bus Structures)

o ISA – Industry System Architecture

o EISA – Enhanced Industry Standard Architecture

o MCA – Micro Channel Architecture

o PCI – Peripheral Component Interconnect

o PCMCIA – Personal Computer Memory Card Industry Association

o VESA – Video Electronic Standard Association

o AGP – Accelerated Graphics Port

o USB – Universal Serial Bus

• Disk Interface

o Floppy Disk Interface

o Hard Disk/CD/DVD Interface

� IDE – Integrated Drive Electronics

� EIDE – Enhanced Integrated

� ATA – Advanced Technology Attachment

• Serial ATA

• Parallel ATA

� SCSI – Small Computer System Interconnect

� RAID – Redundant Array of Inexpensive Disks

• Communication Ports

o Serial

o Parallel

o Keyboard

o Mouse (PS/2)

o Display Port – VGA – Video Graphics Array



• viii. Memory

o ROM

� BIOS (CMOS) – Basic Input Output System

o RAM

� Package wise

• DIP – Dual – In line – Package

• SIMM – Single Inline Memory Module

• DIMM – Dual Inline Memory Module

� Technology wise

• EDO – Extended Data Out

• SD – Synchronous Dynamic

• DDR – Dual Data Rate

• Rambus

Study of motherboards:

• Processor

A processor is the logic circuitry that responds to and processes the basic

instructions that drive a computer. The term processor has generally replaced the term

central processing unit (CPU). The processor in a personal computer or that is embedded

in small devices is often called a microprocessor.

• Processor Slot

The term CPU socket (or CPU slot) is widely used to describe the connector

linking the motherboard to the Processor (CPU(s)) in certain types of desktop and server

computers, particularly those compatible with the Intel x86 architecture. Most CPU

sockets and processors in use today are built around the pin grid array (PGA)

architecture, in which the pins on the underside of the processor are inserted into the

socket. Normally socket is of two types.

o Slot Type

o Socket Type – Zero Insertion Force Socket



To aid installation, zero insertion force (ZIF) sockets are usually used, allowing

the processor to be inserted without any resistance, while gripping the pins firmly once

the processor is in place to ensure a reliable contact. An alternative to the PGA

architecture, used by several current and upcoming sockets, is the land grid array (LGA)

in which the pins reside on the socket rather than the CPU. The pins come into contact

with pads on the bottom of the processor. In contrast to CPU sockets, slot-based

processors and CPUs use a single-edged connection (similar to an expansion slot) rather

than a socket, and slot into the motherboard on their side. Slot architectures are rarely

used today.

• Chip Set

A group of chips on the motherboard that controls the timing and flow of data and

instructions to and from the CPU is known as chip set. One or more chips on a

motherboard that control the data flow between the processor, memory, and the other

components of the system. It consists of following chips.

o Clock Generator

o DMA Controller

• Co – Processor (currently built – in with main processor)

A separate chip (or nowadays, a portion of the CPU) that performs a lot of the

calculations and number crunching for the microprocessor, relieving the CPU of some of

its work and thus enhancing the overall speed of the system.

• Slots for Add – on – Cards (Bus Structures)

A slot is provided for additional cards to be added. Some of the cards are as

follows:-


ISA is an older technology for connecting computer peripherals (stands for

Industry Standard Architecture). Common current devices include modems and sound

cards. ISA is much slower than PCI, so PCI devices are generally better if you have a



choice. ISA is starting to fade and eventually will be removed entirely. Most

motherboards still come with at least one or two ISA slots on them.


(Extended Industry Standard Architecture) This is an enhanced form of ISA,

which allows for 32-bit data transfers, while maintaining support for 8- and 16-bit

expansion boards. However, its bus speed, like ISA, is only 8 MHz. EISA is not widely

used, due to its high cost and complicated nature.


Micro Channel Architecture (hardware) is a 16/32 bits bus developed by IBM in

1986 for its PS/2 machines. It is not successful at all and IBM even uses it only for its

high level systems.


"Peripheral Component Interconnect" is a high-speed connection for devices

including SCSI cards, video cards, sound cards, modems, video capture cards, etc. This is

the primary way of adding devices to your computer. It is faster than ISA, so is preferred

for devices such as sound cards and SCSI cards. It is slower than AGP which is for

graphics cards only, so AGP graphics cards tend to be better than PCI ones. Default PCI

speed is 33 MHz.


Personal Computer Memory Card International Association - A standardized

technology used to develop a expansion for portable devices (ie notebooks) In paging

these credit card sized devices support wireless connectivity. PCMCIA is an organization

consisting of some 500 companies that has developed a standard for small, credit card-

sized devices, called PC Cards. Originally designed for adding memory to portable

computers, the PCMCIA standard has been expanded several times and is now suitable

for many types of devices. There are in fact three types of PCMCIA cards. All three have

the same rectangular size but different widths


Video Electronics Standards Association is a 32-bit local bus standard that is

compatible with both ISA and EISA cards. Many manufacturers of local bus adapters use

this standard because of its speed.




Short for Accelerated Graphics Port, an interface specification developed by Intel

Corporation. AGP is based on PCI, but is designed especially for the throughput demands

of 3-D graphics. Rather than using the PCI bus for graphics data, AGP introduces a

dedicated point-to-point channel so that the graphics controller can directly access main

memory. The AGP channel is 32 bits wide and runs at 66 MHz.


USB is a "plug and play" interface between a computer and add-on devices such

camera and microphone. With USB, a device can be added to your computer without

having to turn the computer off. USB supports a data speed of 12 megabit per second.

This speed will accommodate MPEG video cameras.

• Disk Interface

The disk interface module provides support for handling transfers to and from the disk. It

consists of a priority ordered queue of block descriptors plus a thread that picks the first

descriptor off the queue and submits it to the disk device driver. The block descriptors

used by the disk module are the same as those used by the caches. Mainly there are two

disc interfaces in the mother board.

o Floppy Disk Interface

o Hard Disk/CD/DVD Interface

� IDE – Integrated Drive Electronics

This is a commonly used interface for hard disk drives and CD-ROM drives.

It is less expensive than SCSI, but offers slightly less in terms of performance.

� EIDE – Enhanced Integrated

A hardware interface which is faster than IDE, allows more memory, and can

connect up to four devices (such as hard drives, tape drives, and CD-ROM

drives) to the computer.

� ATA – Advanced Technology Attachment

It is a disk drive implementation that integrates the controller on the disk drive

itself. There are several versions of ATA, all developed by the Small Form

Factor (SFF) Committee: ATA : Also known as IDE (Integrated, or



Intelligent, Drive Electronics) supports one or two hard drives, a 16-bit

interface and PIO modes 0, 1 and 2. ATA-2 : Supports faster PIO modes (3

and 4) and multiword (DMA modes (1 and 2). ... there are two types of ATA.

� Serial ATA

� Parallel ATA

� SCSI – Small Computer System Interconnect

� There are two types of interfaces for hard drives, CD-ROM drives, etc.

One is SCSI, the other is IDE. IDE is much more common and less

expensive. SCSI is more expensive and also more flexible and generally

faster. With a single SCSI card you can have 15 or more devices whereas

you are only allowed to have 4 devices with an IDE system. The fastest

hard drives (and generally CD-ROM drives too) are SCSI-based. ... It is a

standard hardware interface that enables a variety of peripheral devices to

communicate with one another.

� RAID – Redundant Array of Inexpensive Disks

A collection of disk drives that offers increased performance and fault

tolerance. There are a number of different RAID levels. The three most

commonly used are 0, 1, and 5: Level 0: striping without parity (spreading out

blocks of each file across multiple disks). Level 1: disk mirroring or

duplexing. Level 2: bit-level striping with parity Level 3: byte-level striping

with dedicated parity. ... t is a subsystem storage concept designed for the

purpose of offering higher levels of protection from data loss that can occur

from any down time caused by malfunctions compared to the protection

offered by conventional disk drives. RAID arrays composed of conventional

discs can function for hundreds or even thousands of years without losing data

because of a disk failure. ...

• Communication Ports

o Serial

Port, or interface, that can be used for serial communication, in which only 1

bit is transmitted at a time. Most serial ports on personal computers conform

to the RS-232C or RS-422 standards. A serial port is a general-purpose



interface that can be used for almost any type of device, including modems,

mice, and printers (although most printers are connected to a parallel port).

o Parallel

It is an input/output connection on a computer that sends and receives

information in groups of eight bits (binary digits) at a time, traveling at high

speeds along parallel wires to a peripheral device such as a printer. The other

simple connection mechanism is a serial port, which transmits just one bit at a

time -- a data side road compared with a multi-lane motorway.

o Keyboard

o Mouse (PS/2)

o Display Port – VGA – Video Graphics Array

• Memory

o ROM

ROM is used to hold programs and data that must survive when the computer is

turned off. Because ROM is non-volatile; data in ROM will remain unchanged the

next time the computer is turned back on. As the name implies, data cannot be easily

written to ROM; depending on the technology used in the ROM, writing may require

special hardware, or may be impossible. A computer's BIOS may be stored in ROM.

BIOS (CMOS) – Basic Input Output System

BIOS stand for Basic Input/Output System, which controls the interface between

the video card and the computer. However, we are concerned with the System BIOS,

which is a collection of assembly language routines that allow programs and the

components of a PC to communicate with each other at the hardware level. It

therefore works in two directions and is active all the time your computer is switched

on, although these days it is bypassed by almost everything, typically anything 32-bit

in Windows. Software doesn't have to talk to a device directly; it calls a BIOS

routine, which does the job instead. Think of the BIOS as a mini operating system. So

BIOS can also be called Basic Initial Operating System. On an IBM-compatible PC,

you will find the BIOS embedded into a EEPROM on the motherboard, together with

hard disk utilities and a CMOS setup program. The BIOS information’s are stored in

a CMOS chip which is kept under constant voltage supply by the computer backup



battery. This way the information’s contained in the CMOS are always alive even if

the computer power is turned OFF..

PC and motherboard manufacturers make their own BIOSes (such as Compaq,

HCL, ACER etc.), but most tend to be based on code supplied by third party

companies, the most well-known of which are Award, American Megatrends (AMI).

Utilities that come with the BIOS, particularly diagnostic; POST (Power On Self

Test) and low-level format routines for the hard disk. The main menu to the BIOS

setup may contain the following heading: HARD DISK UTILITY or HDD LOW

LEVEL FORMAT. It allows you to low-level format the drive attached to your

computer. After the assembling the system and prior to the software installation the

first thing you have to do as soon as you boot the machine is set the CMOS.

BIOS stand for Basic Input/Output System, although the full term is used very

infrequently. The system BIOS is the lowest-level software in the computer; it acts as

an interface between the hardware (especially the chipset and processor) and the

operating system. The BIOS provides access to the system hardware and enables the

creation of the higher-level operating systems (DOS, Windows 95, etc.) that you use

to run your applications. The BIOS is also responsible for allowing you to control

your computer's hardware settings, for booting up the machine when you turn on the

power or hit the reset button, and various other system functions.

o RAM

Random Access Memory or RAM is a type of computer storage whose contents can

be accessed in any order. This is in contrast to sequential memory devices such as

magnetic tapes, discs and drums, in which the mechanical movement of the storage

medium forces the computer to access data in a fixed order. It is usually implied that

RAM can be both written to and read from, in contrast to Read-Only Memory or

ROM. RAM is categorized into following: -

� Package wise

o DIP – Dual – In line – Package



o SIMM – Single Inline Memory Module

o DIMM – Dual Inline Memory Module

� Technology wise

o EDO – Extended Data Out

o SD – Synchronous Dynamic

o DDR – Dual Data Rate

o Rambus

Types of Computer Expansion Slots [Written by Matthew Elton (copyright 2006

Matthew Elton)]

Expansion slots are located on the motherboard, and openings on the back of the

computer allow the ports on the cards that go in the slots to be accessed. The picture

below shows the SoundBlaster Live sound card, with additional ports attached to it

through an IDE cable. There are several types of expansion slots, including AGP, PCIe

(also known as PCIexpress), PCI, and ISA.

The top card of the SoundBlaster Live sound card plugs into a PCI expansion slot, while

the bottom card sends and receives its data to and from the larger card through an IDE

cable. The smaller card simply needs an empty spot in the case to be mounted to. It does

not need to be placed into an expansion slot on the motherboard.



Types of Expansion Slots:

• ISA

• AGP

• PCI

• PCIe, which is short for PCIexpress

ISA Slots

ISA slots are an older type of expansion slot, twice as big as PCI slots and slower than

PCI slots as well. ISA slots are usually black, while PCI slots are usually white. ISA

slots are not used much anymore, but most computers still have at least one of them.

ISA networking cards, ISA sound cards, ISA video cards, and other types of ISA

expansion cards can be used in the ISA slots.

PCI Slots

The photo above is a picture of a PCI expansion slot, the most common expansion slot.

PCI slots can handle 64 bits of data at a time, twice as fast as ISA slots, which can only

handle 32 bits of data at a time. PCI is an abbreviation for "Peripheral Component

Interconnect." A 64-bit PCI slot has 64 connections to the motherboard, and each

connection is capable of handling 1 bit of data at a time. A 32-bit ISA slot has 32

connections to the motherboard, each handling one bit of data at a time. (Note: Older

technology ISA slots are 8-bit and 16-bit. The newer EISA, (or Extended ISA), slots are

capable of 32-bit data transfer. Older PCI technology is 32-bit. The newer PCI

technology is 64-bit.). The diagram below shows how to properly insert a PCI card into

an empty PCI expansion slot.



As technology changes new expansion cards become available. These include video

cards, which allow a monitor to be connected to the computer, sound cards, which allow

speakers and a microphone to be connected to the computer, and networking cards, which

allow computers to be linked together. There are also many other types of expansion

cards. Below is a photograph of a Promise PCI expansion card. It allows you to connect

up to four additional drives to your computer with IDE cables. This expansion card

provides data transfer rates of up to 66,000,000 bits per second, (or 66Mbs/sec). This

technology is also known as Ultra ATA/66. ATA is an abbreviation for "Advanced

Technology Attachment." Ultra ATA/66 is also known as Ultra DMA/66. DMA is an

abbreviation for "Direct Memory Access." Ultra DMA/66 devices can directly access the

RAM, transferring 66 million bits of data per second.



Below is a picture of Creative Lab’s Sound Blaster Live Value PCI sound card. A sound

card is what processes sound and allows speakers and a microphone to be hooked up to

the computer. When you hear music coming from your computer's speakers, the sound

card's digital signal processor, also known as the DSP, is working together with the

digital-to-analog converter, also known as the DAC, processing and converting digital

sound data (electrical pulses represented by binary code) to analog sound data (increases

and decreases in electrical pulses that the speaker interprets and generates as increases

and decreases in tone, frequency, and volume.) When you talk into your computer's

microphone, the sound card's digital signal processor works along with the analog-to-

digital converter to process and convert analog sound data to digital sound data, which

can be saved onto your computers memory. Record players are analog – they are made

of tiny engravings that the needle moves through, that move back and forth in a wave

shape to change the frequency of the sound. Computers, however, are digital. A music

file stored on a computer hard drive is stored as a series of positive and negatively (north

and south) magnetically charged sectors on the hard drive. These are represented by 1s

and 0s in what is called binary code. Different sequences of these magnetic charges

instruct the computer to perform different tasks, and in this case, tell the computer what

frequencies and volumes to play when playing the music file.



Better sound cards have better sound, however, you can save a ton of money by just

buying a mediocre sound card online (I recommend www.newegg.com for those

interested in buying computer parts – there’s even better deals on neweggs older website,

just click on “Newegg Old Version” or something like that at the top right hand corner of

the homepage of newegg.com) The Sound Blaster Live Value card allows you to connect

a sound input device, like a CD-Player or radio, a microphone, front speakers, rear

speakers, and a joystick or MIDI instrument, like an MIDI keyboard. The front and rear

speakers can be combined together to produce stereo surround sound. Just like the video

card, the sound card uses its own little processor to process sound data.

Below is a picture of a SCSI (pronounced “sscuhzy”) PCI expansion card. SCSI is an

abbreviation for "Small Computer Interface System." With a SCSI expansion card, you

can connect up to fifteen devices to one SCSI connection. SCSI is one of the fastest data

transfer interfaces there is. SCSI cards are available with transfer rates up to 320 MB per

second! The Ultra320 SCSI-3 interface is the fastest SCSI interface, with a 320MB/sec

data transfer rate! Below is a picture of a PCI SCSI expansion card.



AGP Slots

The AGP expansion slot connects AGP video cards to the motherboard. The

video card shown above is an AGP GeForce FX 5500. Video cards are also known as

graphics cards. They process video and image data that will be displayed on your

screen. The monitor plugs into the video card. AGP is an abbreviation for Accelerated



Graphics Port. Most AGP video cards are capable of a higher data transfer rate than PCI

video cards. Video cards, like the one shown above, simply plug into an AGP slot and

connect a monitor or other video display device to a computer, usually through the VGA

port. The video card shown above has three different ports, for three different types of

monitors. The "DVI Out" connector connects to a “digital video display”. DVI is an

abbreviation for Digital Video Interface. Video cards with a TV output connection are

capable of displaying a computer's video on a television instead of a computer monitor,

which is great for playing movies on your computer. Unfortunately, most televisions

only support a very low resolution and refresh rate when hooked up to computers. Video

cards with a TV input connection are able of displaying a television's video on a

computer. This allows you to record television programs onto your computers hard

drive. The VGA connection is the standard connection to most monitors.

The quality of the display depends mostly on the type of video card, but also on

the type of monitor. There are many factors in determining how good a video card is, but

the most important, in my opinion, is video-RAM. Video cards have their own RAM,

called “video-RAM” and the more RAM the video card has the faster the video card, and

your computer, will run. Go to “Display Properties” from the control panel or by right

clicking on your desktop and clicking “Properties” and then click “Settings” and click

“Adapter” to see how much video RAM your current video card has. If you have less

then 128 megabytes of Video-RAM in your desktop, and you play a lot of computer

games, I would highly recommend upgrading to a video card with 128 megabytes of

video-RAM, such as the NVIDIA GeForce MX400 128Mb PCI, which goes in the PCI

expansion slot. I bought it for only fifty dollars online (it’s normally a hundred dollars in

stores but I got a great deal on it from www.newegg.com I recommend

www.newegg.com for those interested in buying computer parts – there’s even better

deals on neweggs older website, just click on “Newegg Old Version” or something like

that at the top right hand corner of the homepage of newegg.com). After upgrading from

a measly eight megabyte video card to the NVIDIA GeForce MX4000 128MB PCI video

card, my computer performed twice as fast! Games that used to take up to fifteen

minutes to load would load in seconds!



Anyway, let’s get back to talking about AGP cards. The photograph below shows what

an AGP expansion slot looks like.

AGP slots and cards come in four different modes, and you must be careful to match the

card and slot with the correct mode. Some AGP cards and AGP slots are capable of

running in more than one mode. AGP 1x mode is the oldest; it transfers data at 266MBs

per second. AGP 2x mode transfers data at 533megabytes per second. AGP 4x mode

transfers data at 1.07 gigabytes (1007 megabytes) per second. The latest AGP mode is

AGP 8x. It transfers data at 2.14gigabytes (2140 megabytes) per second!

Below is a picture of three PCI Express slots.

PCI EXPRESS

PCI Express is a new technology that is slowly replacing AGP. PCI Express x16 slots can

transfer data at 4GBs per second, which is about twice as fast as an AGP 8x slot! PCIe

stands for PCI Express, or PCIexpress. PCI Express slots come in five different sizes and

speeds: PCIe x1, PCIe x2, PCIe x4, PCIe x8, and PCIe x16. PCIe x16 slots are used for

graphics cards.



Monitor Connectors

HD15 15 pins in three rows, pins are skinnier than a usual

"DB" connector, thus it's got an "H" for High Density. Used

for PC's SVGA video cards and monitor cables.

DB15 15 pins in two rows, pins are just

like a DB9 or DB25. Used for Mac

monitors.

BNC connectors are used on Macs, Sun's and just about anything that's old

and good.

DB9 9 pins in two rows, used on older monitors, and VGA's.

PS/2 style Serial ports also use DB9 connectors.

13W3 a bunch of "DB" style pins and

three funny looking coax contacts. Used

on Sun and Mac monitors.

Other PC/Mac connectors

Parallel/Printer

CN36 (female) This is the connector you see on

the back of most printers.

CN36 (male) This is the connector used by most

printer cables.

DB25 (female) This connector is used for

parallel printer output on the PC. It is also used

for SCSI output, especially on the Mac.

DB25 (male) This is used for parallel printers (and

other parallel port devices) as well as SCSI and

serial ports. If you see a male on the back of your



computer, it is usually your COM2 serial port.

HPCN36 male This is the new "Type-C" IEEE-

1284 Parallel port connector which is used on

some new laser printers.

MINIDIN-8 (female) Serial Mac connector. Mac

Printers, Mac printer and modem outputs, etc.

Serial

DB25 serial connector. On a computer, this

would be a male not a female as pictured above.

DB9 serial connectors. On the computer there

should be a "male" connector, the mouse or other

serial device (modem, digital camera) would have a

female.

USB and Firewire connectors

"i.Link" connector. This is basically a 4-pin

Firewire/i.link/IEEE-1394 connector.

"Firewire" connector.This is a 6-pin Firewire/IEEE-

1394 connector.

USB type "A" connector. Connects to computer

or USB Hub.

USB type "B" connector. Connects to peripheral or

to USB Hub.



Mini USB connector used on many new USB

digital cameras.

Mini USB 2.0 connector used on many new USB

digital cameras.

Other connectors

S-Video connector, sometimes called S-VHS or

Y/C video. There're 4 little pins in there, it's

called a DIN4.

RCA (above) connector. Standard stereo connector.

3.5 mm Mini Phone Plug connector, (below) used on

computer sound cards.

SC connector, fiber optic network connector.

ST connector, fiber optic network connector.

MTRJ fiber optic network connector.

Toslink connector. Used for digital audio.

Different types of ports:

Ports are used to connect external devices to the computer. There exist several types of

ports like serial port, parallel port, USB port, AGP port. As the name suggests, the serial

port transfers data serially a bit at a time. As a result, the serial port needs only wire to

transmit 8 bits. The disadvantage is that it takes 8 times longer to transmit a byte. Also, it

is necessary to send a start bit before each byte of data, a stop bit after the byte to mark

the end of byte and a parity bit to help check the integrity of data. Serial ports come in the

form of 9-pin or 25-pin male connector. Serial ports are often known as communication

ports or RS232C ports. They are typically used to connect devices like mouse and

modem.

Parallel ports can send or receive a byte (8-bit) at a time. Unlike the serial port, these 8-



bits are transmitted parallel to each other. Parallel ports come in the form of 25-pin

female connector. Parallel ports are popularly used to connect printer, scanner, CD writer,

zip drive, external hard disk drive, tape backup drive, etc.

To spare the user botheration of 8-pin, 25-pin, male, female connectors, the USB has

been designed. It gives you a single, standardized, easy-to-use way to connect up to 127

devices to a computer. These devices include printers, scanners, mice, joystick, digital

camera, web cameras, speakers, telephones, zip drives, network connections, scientific

data acquisition devices, etc.

The AGP (Accelerated Graphics Port) port is used to connect to graphic card that

provides high-speed video performance typically required in games and other multimedia

applications.

Different types of add on cards:


ISA is an older technology for connecting computer peripherals (stands for

Industry Standard Architecture). Common current devices include modems and sound

cards. ISA is much slower than PCI, so PCI devices are generally better if you have a

choice. ISA is starting to fade and eventually will be removed entirely. Most

motherboards still come with at least one or two ISA slots on them.


(Extended Industry Standard Architecture) This is an enhanced form of ISA,

which allows for 32-bit data transfers, while maintaining support for 8- and 16-bit

expansion boards. However, its bus speed, like ISA, is only 8 MHz. EISA is not widely

used, due to its high cost and complicated nature.


Micro Channel Architecture (hardware) 16/32 bits bus developed by IBM in 1986

for its PS/2 machines. It is not successful at all and IBM even uses it only for its high

level systems.


"Peripheral Component Interconnect" is a high-speed connection for devices

including SCSI cards, video cards, sound cards, modems, video capture cards, etc. This is



the primary way of adding devices to your computer. It is faster than ISA, so is preferred

for devices such as sound cards and SCSI cards. It is slower than AGP which is for

graphics cards only, so AGP graphics cards tend to be better than PCI ones. Default PCI

speed is 33 MHz.


Personal Computer Memory Card International Association - A standardized

technology used to develop a expansion for portable devices (ie notebooks) In paging

these credit card sized devices support wireless connectivity. PCMCIA is an organization

consisting of some 500 companies that has developed a standard for small, credit card-

sized devices, called PC Cards. Originally designed for adding memory to portable

computers, the PCMCIA standard has been expanded several times and is now suitable

for many types of devices. There are in fact three types of PCMCIA cards. All three have

the same rectangular size but different widths


Video Electronics Standards Association is a 32-bit local bus standard that is

compatible with both ISA and EISA cards. Many manufacturers of local bus adapters use

this standard because of its speed.


Short for Accelerated Graphics Port, an interface specification developed by Intel

Corporation. AGP is based on PCI, but is designed especially for the throughput demands

of 3-D graphics. Rather than using the PCI bus for graphics data, AGP introduces a

dedicated point-to-point channel so that the graphics controller can directly access main

memory. The AGP channel is 32 bits wide and runs at 66 MHz.


USB is a "plug and play" interface between a computer and add-on devices such

camera and microphone. With USB, a device can be added to your computer without

having to turn the computer off. USB supports a data speed of 12 megabit per second.

This speed will accommodate MPEG video cameras.



Power supply in PC:

If there is any one component that is absolutely vital to the operation of a computer, it is

the power supply. Without it, a computer is just an inert box full of plastic and metal. The

power supply converts the alternating current (AC) line from your home to the direct

current (DC) needed by the personal computer. In this article, we'll learn how PC power

supplies work and what the wattage ratings mean.

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Power Supply

In a personal computer (PC), the power supply is the metal box usually found in a corner

of the case. The power supply is visible from the back of many systems because it

contains the power-cord receptacle and the cooling fan.

Power supplies, often referred to as "switching power supplies", use switcher technology

to convert the AC input to lower DC voltages. The typical voltages supplied are:

• 3.3 volts

• 5 volts

• 12 volts

The 3.3- and 5-volts are typically used by digital circuits, while the 12-volt is used to run

motors in disk drives and fans. The main specification of a power supply is in watts. A

watt is the product of the voltage in volts and the current in amperes or amps. If you

have been around PCs for many years, you probably remember that the original PCs had

large red toggle switches that had a good bit of heft to them. When you turned the PC on

or off, you knew you were doing it. These switches actually controlled the flow of 120

volt power to the power supply.

Today you turn on the power with a little push button, and you turn off the machine with

a menu option. These capabilities were added to standard power supplies several years

ago. The operating system can send a signal to the power supply to tell it to turn off. The

push button sends a 5-volt signal to the power supply to tell it when to turn on. The



power supply also has a circuit that supplies 5 volts, called VSB for "standby voltage"

even when it is officially "off", so that the button will work.

This is a power supply removed from its PC case. The small, red

switch at right, above the power-cord connector, is for changing line

voltages in various countries.

The interior of a power supply.



Switcher Technology

Prior to 1980 or so, power supplies tended to be heavy and bulky. They used large, heavy

transformers and huge capacitors (some as large as soda cans) to convert line voltage at

120 volts and 60 hertz into 5 volts and 12 volts DC.

The switching power supplies used today are much smaller and lighter. They convert the

60-Hertz (Hz, or cycles per second) current to a much higher frequency, meaning more

cycles per second. This conversion enables a small, lightweight transformer in the power

supply to do the actual voltage step-down from 110 volts (or 220 in certain countries) to

the voltage needed by the particular computer component. The higher-frequency AC

current provided by a switcher supply is also easier to rectify and filter compared to the

original 60-Hz AC line voltage, reducing the variances in voltage for the sensitive

electronic components in the computer.

In this photo you can see three small transformers (yellow) in the

center. To the left are two cylindrical capacitors. The large finned

pieces of aluminum are heat sinks. The left heat sink has transistors

attached to it. These are the transistors in charge of doing the

switching -- they provide high-frequency power to the transformers.

Attached to the right heat sink are diodes that rectify AC signals and

turn them into DC signals.



A switcher power supply draws only the power it needs from the AC line. The typical

voltages and current provided by a power supply are shown on the label on a power

supply.

Personal computer power supply label.

VSB is the standby voltage provided to the power

switch.

Switcher technology is also used to make AC from DC, as found in many of the

automobile power inverters used to run AC appliances in an automobile and in

uninterruptible power supplies. Switcher technology in automotive power inverters

changes the direct current from the auto battery into alternating current. The transformer

uses alternating current to make the transformer in the inverter step the voltage up to that

of household appliances (120 VAC).

How an SMPS works



Block diagram of a mains operated AC-DC SMPS with output voltage regulation.

Input rectifier stage

AC, half-wave and full wave rectified signals

If the SMPS has an AC input, then its first job is to convert the input to DC. This is called

rectification. The rectifier circuit can be configured as a voltage doubler by the addition

of a switch operated either manually or automatically. This is a feature of larger supplies

to permit operation from nominally 120 volt or 240 volt supplies. The rectifier produces

an unregulated DC voltage which is then sent to a large filter capacitor. The current

drawn from the mains supply by this rectifier circuit occurs in short pulses around the AC



voltage peaks. These pulses have significant high frequency energy which reduces the

power factor. Special control techniques can be employed by the following SMPS to

force the average input current to follow the sinusoidal shape of the AC input voltage

thus the designer should try correcting the power factor. A SMPS with a DC input does

not require this stage. A SMPS designed for AC input can often be run from a DC supply,

as the DC passes through the rectifier stage unchanged. (The user should check the

manual before trying this, though most supplies are quite capable of such operation even

though no clue is provided in the manual!)

If an input range switch is used, the rectifier stage is usually configured to operate as a

voltage doubler when operating on the low voltage (~120 VAC) range and as a straight

rectifier when operating on the high voltage (~240 VAC) range. If an input range switch

is not used, then a full-wave rectifier is usually used and the downstream inverter stage is

simply designed to be flexible enough to accept the wide range of dc voltages that will be

produced by the rectifier stage. In higher-power SMPSs, some form of automatic range

switching may be used.

Inverter stage

The inverter stage converts DC, whether directly from the input or from the rectifier stage

described above, to AC by running it through a power oscillator, whose output

transformer is very small with few windings at a frequency of tens or hundreds of

kilohertz (kHz). The frequency is usually chosen to be above 20 kHz, to make it

inaudible to humans. The output voltage is optically coupled to the input and thus very

tightly controlled. The switching is implemented as a multistage (to achieve high gain)

MOSFETs amplifier. MOSFETs are a type of transistor with a low on-resistance and a

high current-handling capacity. This section refers to the block marked "Chopper" in the

block diagram.

Voltage converter and output rectifier

If the output is required to be isolated from the input, as is usually the case in mains

power supplies, the inverted AC is used to drive the primary winding of a high-frequency

transformer. This converts the voltage up or down to the required output level on its

secondary winding. The output transformer in the block diagram serves this purpose.



If a DC output is required, the AC output from the transformer is rectified. For output

voltages above ten volts or so, ordinary silicon diodes are commonly used. For lower

voltages, Schottky diodes are commonly used as the rectifier elements; they have the

advantages of faster recovery times than silicon diodes (allowing low-loss operation at

higher frequencies) and a lower voltage drop when conducting. For even lower output

voltages, MOSFET transistors may be used as synchronous rectifiers; compared to

Schottky diodes, these have even lower "on"-state voltage drops.

The rectified output is then smoothed by a filter consisting of inductors and capacitors.

For higher switching frequencies, components with lower capacitance and inductance are

needed.

Simpler, non-isolated power supplies contain an inductor instead of a transformer. This

type includes boost converters, buck converters, and the so called buck-boost converters.

These belong to the simplest class of single input, single output converters which utilise

one inductor and one active switch (MOSFET). The buck converter reduces the input

voltage, in direct proportion, to the ratio of the active switch "on" time to the total

switching period, called the Duty Ratio. For example an ideal buck converter with a 10V

input operating at a duty ratio of 50% will produce an average output voltage of 5V. A

feedback control loop is employed to maintain (regulate) the output voltage by varying

the duty ratio to compensate for variations in input voltage. The output voltage of a boost

converter is always greater than the input voltage and the buck-boost output voltage is

inverted but can be greater than, equal to, or less than the magnitude of its input voltage.

There are many variations and extensions to this class of converters but these three form

the basis of almost all isolated and non-isolated DC to DC converters. By adding a

second inductor the Ćuk and SEPIC converters can be implemented or by adding

additional active switches various bridge converters can be realised.

Other types of SMPS use a capacitor-diode voltage multiplier instead of inductors and

transformers. These are mostly used for generating high voltages at low currents. The low

voltage variant is called charge pump.

Regulation

A feedback circuit monitors the output voltage and compares it with a reference voltage,

which is set manually or electronically to the desired output. If there is an error in the



output voltage, the feedback circuit compensates by adjusting the timing with which the

MOSFETs are switched on and off. This part of the power supply is called the switching

regulator. The "Chopper controller" shown in the block diagram serves this purpose.

Depending on design/safety requirements, the controller may or may not contain an

isolation mechanism (such as opto-couplers) to isolate it from the DC output. Switching

supplies in computers, TVs and VCRs have these opto-couplers to tightly control the

output voltage.

Open-loop regulators do not have a feedback circuit. Instead, they rely on feeding a

constant voltage to the input of the transformer or inductor, and assume that the output

will be correct. Regulated designs work against the parasitic capacity of the transformer

or coil, monopolar designs also against the magnetic hysteresis of the core.

The feedback circuit needs power to run before it can generate power, so an additional

non-switching power-supply for stand-by is added.

Power factor

Early switched mode power supplies incorporated a simple full wave rectifier connected

to a large energy storing capacitor. Such SMPS draws current from the AC line in short

pulses when the mains instantaneous voltage exceeds the voltage across this capacitor.

During the remaining portion of the AC cycle the capacitor provides energy to the power

supply. As the result, input current of such basic switched mode power supplies has high

harmonics content and relatively low power factor. This creates extra load on utility lines,

increases heating of the utility transformers, and may cause stability problems in some

applications such as in emergency generator systems or aircraft generators. In 2001 the

European Union put into effect the standard IEC/EN61000-3-2 to set limits on the

harmonics of the AC input current up to the 40th harmonic for equipment above 75W.

The standard defines four classes of equipment depending on its type and current

waveform. The most rigorous limits (class D) are established for personal computers,

computer monitors, and TV receivers. In order to comply with these requirements

modern switched-mode power supplies normally include an additional power factor

correction (PFC) stage.

Types

Switched-mode power supplies can be classified according to the circuit topology.



• Buck converter (single inductor; output voltage < input voltage)

• Boost converter (single inductor; output voltage > input voltage)

• buck-boost converter (single inductor; output voltage can be more or less than the

input voltage)

• flyback converter (uses output transformer; allows multiple outputs and input-to-

output isolation)

o typical Power: 0 to ca. 150 W

o relative cost: 100%

Applications

Switched-mode PSUs in domestic products such as personal computers often have

universal inputs, meaning that they can accept power from most mains supplies

throughout the world, with rated frequencies from 50 Hz to 60 Hz and voltages from 100

V to 240 V (although a manual voltage "range" switch may be required). In practice they

will operate from a much wider frequency range and often from a DC supply as well. In

2006, Intel proposed the use of a single 12 V supply inside PCs, due to the high

efficiency of switch mode supplies directly on the PCB.

Cars, trucks, telecom lines, and production plants, but not planes, supply DC to avoid

hum and ease the integration of capacitors and batteries used to buffer the voltage.

In the case of TV sets, for example, one can test the excellent regulation of the power

supply by using a variac. For example, in some models made by Philips, the power

supply starts when the voltage reaches around 90 volts. From there, one can change the

voltage with the variac, and go as low as 40 volts and as high as 260, and the image will

show absolutely no alterations.

PCH Module 1

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Transcript of PCH Module 1