Transcript Document
Overview
In this chapter, you will learn to
Explain how motherboards work
Identify the types of motherboards
Explain chipset varieties
Motherboard
Provides foundation for PC
Every piece of H/W , from
CPU to expansion card
directly Example?
or indirectly plugs into it.
Example?
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Motherboard
Motherboards are officially printed circuit boards (PCBs)
PCBs come in multiple layers
with highways of wires
(bus systems) in the layers
These highways of wires are
called traces
Holds the vast majority of the ports
used by peripherals
and it distributes powers from power
supply .
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Motherboard Characteristics
Three interrelated characteristics define modern
motherboards :
Form Factor defines
› Physical Size of the motherboard.
› General location of components and parts.
Chipset defines
› Type of processor and RAM supported.
› Determine the internal and external devices supported by
the motherboard.
Built-in components
› Determine the core functionality of the system.
Form Factors
Industry standardized shapes and layouts that enable
motherboards to work with cases and power supplies.
A single form factor applies to all 3 components
(motherboard, power supply, and case).
You need to install a motherboard in a case designed to fit it, so
ports and slot opening in the back fit correctly
Power supply and motherboard need
matching connectors.
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Form Factors
The PC industry construct a number of form factors
over the years with name such as:
AT
ATX
BTX
And others.
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AT Form Factor
Used P8 and P9 connectors to power the motherboard
Single keyboard DIN or (PS\1) connector
Lack of external ports
Distinguished by position of the keyboard
plug and power socket
Now: obsolete
Has a few size variations:
Baby AT is the most common (Pentium)
Full AT
LPX and NLX.
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Baby AT Motherboard
Single keyboard
DIN connector
Lack of external
ports
Power supply
connector
Small size
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ATX Form Factor
Created in 1995
Improves four main areas over AT.
Replace DIN port in AT with rear panel that has all necessary
ports built in.
Better air movement
Easier access of RAM and CPU
Enhanced
performance: by placing RAM closer to
Northbridge and CPU.
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Uses soft power to turn PC on/off through software.
ATX Form Factor
Uses Single 20-pin P1 power connector instead of P8 and
P9.
Variations (smaller versions of ATX):
Micro ATX
and Flex ATX.
Many techs and web sites use the term mini-ATX to
describe these boards
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ATX Form Factor
Each main type of form factor requires its own cases.
AT Motherboard go into AT cases.
NLX Motherboard go into NLX cases.
Therefore, you can not replace one form factor with
another without purchasing a new case.
Exception: larger form factor ATX cases can handle any
smaller-sized form factor
motherboard.
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ATX Motherboard Parts
AT and ATX Boards
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Power Supply Connectors
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System Board (Pentium)
Baby AT: 1- PS connector. 2- single DIN 3- Size
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System Board (Pentium II)
ATX: 1- PS connector. 2- rear panel
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BTX Form Factor
BTX (Balanced Technology Extended)
Due to heat, cooler form factors needed
Three subtypes of BTX
› BTX
designed to replace ATX
› microBTX
designed to replace microATX
› picoBTX
designed to replace FlexATX
Its look like ATX but you can not put a BTX
motherboard in an ATX case. Why?
BTX does not change the power connection, so there
is no such thing as a BTX power supply.
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BTX Form Factor & Thermal Unit
CPU moved to front of Motherboard
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The Chipset
Serves as electronic interfaces through which the (CPU,
RAM, and input/output devices) interact. Like what?
RAM
I/O
Chipsets
CPU
Several Chipset Varies in feature, performance and
stability.
Composed of :
Northbridge high speed interfaces like video card RAM
and Southbridge
low speed devices such as USB
controller and hard drive controller keyboard controller. 20
The Chipset
Northbridge:
Helps the CPU work with RAM and video (on Intel-based
systems).
Communicates with video card on newer AMD systems.
Why?
Therefore they do a lot and get hot so they get their
own heat sink and fan assembly.
Southbridge:
handles some expansion devices and mass storage drives.
Don’t need extra cooling.
Modern Southbridge do not support old devices
(floppy drive, parallel port, modem,..). A third chip
called Super I/O chip (not part of chipset) handle
them.
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The Chipset
Not always called Northbridge and Southbridge
Intel-based motherboards may refer to them as:
Memory Controller Hub (MCH) for Northbridge
and I/O Controller Hub (ICH) for Southbridge.
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The Chipset
The system ROM chip provides part of the BIOS for
the chipset. It is not sufficient.
You have to load the proper drivers for the specific OS
to support all features of today’s chipsets.
All motherboard ship with a CD-ROM disc with
drivers.
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Chip Set Manufacturers
Some of the companies produce chipset designed for
both Intel and AMD CPUs whereas others choose one
or the other company to support.
Intel Corporation
AMD, Inc.
VIA Technology, Inc.
NVDIA corporation
SiS
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How it all connects together
backside bus
L2 Cache
Pentium
CPU
(in the CPU
housing – on die)
32 bit address bus
64 bit data bus
RAM
memory bus
HDD
EIDE
frontside bus
L1 cache
North
Bridge
The Chipset
(Memory Controller)
extends the bus to AGP bus
every device on
the PC.
AGP
scanner
PCI
South Bridge
PCI bus
CD/DVD
sound
ISA bus
keyboard
mouse
modem
FDD
ISA
BIOS
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Motherboard Components
Connections and capabilities of a motherboard
sometimes differ from its chipset. How?
Not all chipset features may be supported with ports
(for cost savings)
Also a motherboard maker may choose
to install extra features
USB / FireWire page 237 (exercise)
Sound page 238 (exercise)
RAID page 238 (exercise)
AMR/CNR page 238 (exercise)
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Overview
In this chapter, you will learn to
Explain Read Only Memory
Explain the function of BIOS
Distinguish among various CMOS setup utility options
Describe BIOS and device drivers
What is (ROM)?
Read Only Memory
Memory chips that contain data, instructions, or
information that is recorded permanently.
Data can only be read, cannot be modified
Nonvolatile — Contents not lost when the computer is
turned off
Program stored on ROM are known as firmware not a
Software.
Read Only Memory (ROM)
ROM have different type:
ROM
PROM
Programmable Read-Only Memory (only once)
Blank ROM on which you can place items permanently
EPROM
Erasable PROM by Ultraviolet (every time you want)
EEPROM
Electrically Erasable PROM
A type of PROM containing microcode that a
programmer can erase using electricity.
What is Flash Memory?
Variation of EEPROM
Also called flash ROM or flash RAM
Nonvolatile memory that can be erased electronically
and reprogrammed.
Stores data and programs on many handheld
computers and devices such as Camera and mobile
phone.
Flash memory cards
store flash memory on
removable devices
instead of chips
We Need to Talk
Placing a number of components into a computer is
useless if CPU can not communicate with them.
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Northbridge & Southbridge
Bridges (North, South) connect the devices
CPU uses address bus to talk to devices
But , How does it know what to say to them?
Keyboard
controller
chip
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Basic Input Output Services
A special kind of Program is required to enable the CPU
to talk to other devices
These programs are collectively known as the basic
input/output service (BIOS)
A Flash ROM chip stores these programs Why?
When CPU wants to talk to KB controller, it goes to BIOS
ROM chip to access the proper program.
Similar to
codebook
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BIOS
Basic Input Output Services
Permanently stored on ROM chip called System ROM or
System BIOS
Contains small programs - each program is called a
service- that enable CPU to
Communicate with the devices (keyboard, floppy, hard
drive, monitor, …)
They are necessary to start the computer
load the operating system
and other files when you first turn on the computer
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BIOS
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ROM BIOS
There is One ROM chip on the system board that contains
BIOS.
Modern motherboards use Flash ROM (you can change the
contents through a very specific process called “flashing the
ROM”) Read about it in book P180
There exists hundreds of little services (2 to 30 lines of
code each)for communicating with floppy drives, hard
drives, …
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System BIOS
ROM chips can store 2 MB although only 65,536 bytes
system are used to store system BIOS.
Every system BIOS has two types of hardware to support.
First:
All hardware that never changes.
Ex: KB, PC speaker.
You cannot change keyboard controller chip.
Second:
All hardware that might change.
Ex: RAM (you could add RAM), hard drives (replacing/
adding).
The system ROM stores the BIOS for them, but it needs
another place to store information about the specific details of
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them CMOS
CMOS
A separate memory chip, called Complementary Metal-
Oxide Semiconductor (CMOS) chip stores the
information that describes specific device parameters.
CMOS does not store programs, only data that is read by
BIOS to be able to talk to the changeable hardware.
CMOS also acts as a clock to keep date and time
Years ago: CMOS was in separate chip.
Today: CMOS is built into Southbridge.
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CMOS
CMOS can store up to 64KB of data but usually only
uses about 128 bytes
CMOS chip is volatile (kept alive by battery). This
way the information contained in the CMOS are
always present even if the computer power is
turned off.
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CMOS
Stores only changeable data.
Customizable via SETUP program.
If data in CMOS about certain hardware is different
from its actual specs, PC can not access that
hardware.
If
you change one of changeable devices,
parameters have to be changed in CMOS how to
change data on CMOS?
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CMOS SETUP Program
Special program that allows you to access and update
CMOS data
Stored on system ROM (BIOS)
Companies that write the BIOS and how to access
CMOS at boot:
Phoenix Technologies - Ctrl Alt Esc
Award Software - uses DEL key
American Megatrends (AMI) - DEL key
Other key combinations are: Ctrl Alt Ins, Ctrl A, Ctrl S,
Ctrl F1, or F10
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Accessing Award SETUP
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CMOS setup program
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CMOS setup program
Exercise: how to access CMOS setup on your PC and
what are the available options?
Caution: it is perfectly fine to access the CMOS setup
program, but do not make changes unless you fully
understand the system
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BIOS and device drivers
PC designers understood that they could not anticipate
every new type of H/W.
Therefore, they gave us ways to add programs for new
devices other than on the BIOS. It is called BYOB
(Bring Your Own BIOS)
Ex: Mice, Sound cards,….
Two ways to BYOB:
Option ROM (hardware solution)
and device driver (software solution)
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Option ROM
Embedded the BIOS in a ROM on the hardware device
itself.
Today only video card contains its own BIOS.
Most devices use more flexible software method (device
derivers).
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Device drivers
A device driver is a file that contains the BIOS commands
necessary to communicate with the devices they support
stored on the PC’s hard drive.
Operating system loads these drivers into RAM when
booting
They come with the device - in a CD- when you buy it.
The generic name for CD is installation disc
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Registry
A special database –used by windows- that stores
everything you want to know about your system,
including device drivers.
Use device manager utility to access registry. You can
manually change/remove and drivers
Exercise: how to use device manager?
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Device Manger
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POST
The power-on self test (POST) is a special program stored
on the ROM chip (BIOS)
Initiated when the computer is turned on or is reset
Checks out the system every time the computer boots
POST program sends out a standard command that says
to all the devices “check yourselves out”.
All standard devices run their own internal diagnostics.
Quality?
PCs convey POST information to user in two ways:
beep codes
or text message (more useful)
Exercise: study more about beep codes and text message
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System ROM Responsibility
System ROM contains:
BIOS routines
CMOS setup program
POST
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Basic Boot Process (Step)
Once the power is turned on, the PC “pulls itself up by
its bootstraps”
First component to wake up is the CPU.
By reads a special wire called power good wire once the
power supply provides the certain voltage to the CPU
Built in memory address is sent on address bus.
This address represent the first line of POST program on
the system ROM
POST is run
If problem happen beep code or text message displayed.
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Boot Process
After POST finishes, it passes control to last BIOS
function: the bootstrap loader. Its job is to find the
operating system.
The bootstrap loader loads the operating system from
the boot sector (In hard drive implementation chapter)
Searches the floppy, CD-ROM, or the hard drive
Boot order set in CMOS
It reads CMOS to tell it where to look first for
operating system (boot order).
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Boot Process
If the device is bootable (called system disk), its boot
sector will contain special programming designed to
tell the system where to locate the operating system.
If bootstrap loader locates a good boot sector, it passes
control to operating system and removes itself from
memory.
Otherwise it goes to next device specified in CMOS.
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Care and Feeding of CMOS
If CMOS battery run out of charge, you lose CMOS
information and computer will not boot.
Any PC made after 2002 will boot to factory default if
the CMOS clears but you will still get error at boot
CMOS configuration mismatch
CMOS date/time not set
No boot device available
CMOS battery state low. HOW to replace it?
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Care and Feeding of CMOS
Common reasons for losing CMOS data
On-board battery runs out
Pulling and inserting cards
Touching the motherboard
Dropping something on the motherboard
Dirt on the motherboard
Faulty power supplies
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Fix Problem
To fix these problems:
Have CMOS setting memorized
Replace the battery.
Compare current settings to backup copy
CMOS save and restore program - CMOSSAVE.
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Clearing CMOS Settings
To clear the CMOS settings, place the shunt on
the CMOS jumper
Resets to factory settings
Resets password
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