The document discusses motherboards and BIOS. It explains that the motherboard provides the foundation for the PC and acts as the central connecting point. The BIOS stored in ROM allows the CPU to communicate with devices. It discusses chipsets, form factors, boot processes, and how the CMOS stores configurable settings to customize a system.

2. Overview
 In this chapter, you will learn to
 Explain how motherboards work
 Identify the types of motherboards
 Explain chipset varieties

3. Motherboard
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 Provides foundation for PC
 Every piece of H/W , from
CPU to expansion card
 directly Example?
 or indirectly plugs into it.
Example?

4. 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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5. 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.

6. Form Factors
 Industry standardized shapes and layouts that enable
motherboards to work with cases and power supplies.
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 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.

7. Form Factors
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 The PC industry construct a number of form factors
over the years with name such as:
 AT
 ATX
 BTX
 And others.

8. AT Form Factor
 Used P8 and P9 connectors to power the motherboard
 Single keyboard DIN or (PS1) 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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9. Baby AT Motherboard
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Single keyboard
DIN connector
Lack of external
ports
Power supply
connector
Small size

10. 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.
 Uses soft power to turn PC on/off through software. 10

11. 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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12. 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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13. ATX Motherboard Parts

14. AT and ATX Boards
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15. Power Supply Connectors
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16. 16
Baby AT: 1- PS connector. 2- single DIN 3- Size

17. 17
ATX: 1- PS connector. 2- rear panel

18. 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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19. BTX Form Factor & Thermal Unit
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CPU moved to front of Motherboard

20. The Chipset
 Serves as electronic interfaces through which the (CPU,
RAM, and input/output devices) interact. Like what?
 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
Chipsets
RAM CPU
I/O

21. 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. 21

22. 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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23. The Chipset
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 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.

24. 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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25. 25
Pentium
CPU
North Bridge
(Memory Controller)
32 bit address bus
64 bit data bus
frontside bus
L2 Cache
(in the CPU
housing – on die)
backside bus
L1 cache
RAM
memory bus
AGP
AGP bus
South Bridge PCI
PCI bus
scanner
modem
sound
EIDE
ISA
ISA bus
keyboard
mouse
FDD
BIOS
HDD
CD/DVD
How it all connects together
The Chipset
extends the bus to
every device on
the PC.

26. 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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27. 27

28. 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

29. 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.

30. 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.

31. 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

32. We Need to Talk
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Placing a number of components into a computer is
useless if CPU can not communicate with them.

33. Northbridge & Southbridge
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 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

34. Basic Input Output Services
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 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

35. 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 computer35

36. 36

37. 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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38. 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
them CMOS 38

39. 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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40. 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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41. 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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42. 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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43. Accessing Award SETUP
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44. CMOS setup program
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45. 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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46. 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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47. Option ROM
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 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).

48. 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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49. 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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50. 50
Device Manger

51. 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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52. System ROM Responsibility
 System ROM contains:
 BIOS routines
 CMOS setup program
 POST
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53. 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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54. 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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55. 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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56. 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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57. 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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58. 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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59. Clearing CMOS Settings
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 To clear the CMOS settings, place the shunt on
the CMOS jumper
 Resets to factory settings
 Resets password