1. Motherboards
Chapter 3

3. Motherboards
Motherboard is considered the most important element of a computer’s design
Provides a physical surface on which to mount electronic components such as resistors, capacitors, chips, slots and sockets
Provides a means for expanding and customizing they system by inserting expansion boards into slots
Also referred to as the system board, main board, and planar board

4. Motherboards (cont’d)
The electrical circuits that run across the surface of the motherboard are called traces
A collection of traces and conductors is called a bus. There are many types of busses
Data bus (Buss width of 8,16,32, and64 bit buss)
Control bus – activates devices i.e. hard drive
Power bus – sends electrical power to low consumption devices
Internal bus – integrated circuit inside CPU
Memory bus – connect CPU to RAM
I/O bus (expansion buss) CPU to expansion slots

5. Motherboards (cont’d)
A collection of busses is also called a bus
The Local bus consists of the power bus, data bus, control bus, and the memory bus
Local bus is also called memory bus, system bus or front side bus (FSB)
The back side bus describes the CPU internal bus

6. Form Factors
Form factor: (footprint) The physical shape or outline of the motherboard
Must be considered when upgrading a PC
Power supply must match the motherboard
XT, AT and Baby AT
XT Original IBM PC (1983) 8-bit
AT slightly larger than XT 16-bit
Baby AT same size as XT but 16-bit

7. Form Factors (cont’d) ATX (popular until 1996)
Most common form factor for full-size computers
Looks like Baby ATX turned 90 degree
Polarized power supply connector*
Requires special shaped power supply
Three common sizes
ATX – 12.0” x 9.6”
Micro ATX – 9.6” x 9.6”
Flex ATX – 7.5” x 9.6”

8. Form Factors (cont’d) Mini ITX: Smaller version of the micro ATX
Used for small desktop computers and mobile devices
Mini ITX - 6.7” x 6.7”
Nano ITX - 4.7” x 4.7”
Pico ITX ” x 2.83”
Mobile ITX ” x 2.36”

9. Form Factors (cont’d)
LPX designed for low profile desktop or slim towers
Does not have expansion slots
Single expansion slot mounted in the center of the board
Single slot host a bus riser card
Popular in low priced computers
Not standard, proprietary center slot is not always is same place

10. LPX Motherboard

11. Form Factors (cont’d)
NLX Uses a bus riser card but it is located at the end of the board (the edge of the board actually plugs into the riser card)
Standardized
Sized 9.0” x 10”-13.6”
Used in Gateway, HP, IBM,NEC and Micron
BTX Designed to help cool CPU by placing it right by fan
Reduced Number of Fans and noise
Obsolete case
BTX 10.5 x 12.8
Micro BTX 10.5 x 10.4
Nano BTX 10.5 x 8.8
Pico BTX 10.5 x 8.0

12. NLX Motherboard

13. Form Factors (cont’d)
Backplane: a circuit board with an abundance of slots along the length of the board.
Not a true form factor
Used in heavy industry
There are two types of Backplanes:
Passive: all typical motherboard circuits and chips are located on the expansion boards
Active: contains the usual circuits and chips normally found on a motherboard

14. Backplane

15. Bus System Architecture
Originally computers had one bus. It ran at same speed as the CPU
As CPU speeds increased high speed frequency increase inductive reactance occurred with in the bus system.
Inductive reactance magnetic or radio interference actually chokes electron flow.
Twisted pairs counteracts IR
Length of wires actually affect data transfer speed

16. Bus System Architecture
Chipsets manage buses of different frequencies
Originally two chipsets were used:
North chipset close to CPU connect high speed devices to CPU (called north bridge)
South chipset connect low speed devices (south bridge)
Intel phased out North and south bridge and replaced it with Quick Path Interconnect (QPI)
AMD phased out and replaced it with HyperTransport Technologies

17. Bus System Architecture (cont’d)
Without chipsets the CPU would be required to handle all computer data transfers thus slowing is down.
Chipsets enable expansion slots
Chipsets are an integral part of the motherboard and are not field replaceable.
If a chipset the entire motherboard must be replaced

18. Expansion Card Slots
Expansion card slots provide a quick and easy method of connecting devices directly to the motherboard by accepting adapters, expansion cards, interface cards, and daughter boards
Most common expansion slots are PCI Express
USB and IEEE-1394 (firewire) not true slots but act like one

19. Expansion Card Slots (cont’d)
Peripheral Components Interconnect (PCI)
32 Bit
66 MHz
132 MBps
PCI-X
64 Bit
266 MHz
17 Gbps
PCI Express (PCI-E)
533 MHZ
34 Gbps
Serial

20. Expansion Card Slots (cont’d)
MiniPCI and MiniPCIe: smaller versions of full size PCI and PCIe designed for laptops, notebooks and other portable devices
IEEE-1394 (Firewire): like USB eliminate the need for expansion slots, parallel ports and serial ports.
USB is pushing it out of the market
Can be added with an expansion card.

21. Expansion Card Slots (cont’d)
Universal Service Bus (USB) designed to replace any expansion slot except high data rate video expansion slot.
Allows addition of devices without opening case
Can support 127 devices
Plug and play
Devices take turns communicating through USB port, sending ‘packets’ of data like a network
USB Mbps (data one way at a time - half duplex)
USB Gbps (data flow both ways at one – full duplex)

22. Expansion Card Slots (cont’d)
USB Cables:
USB wires:
2 data (twisted pair)
2 Power
USB wires:
2 USB 2.0 data (twisted pair)
2 USB 3.0 data receive (twisted pair)
2 USB 3.0 data transmit (twisted pair)
1 5 volts (+)
1 power ground (-)
1 electrical ground for signal (-)
1 electrical ground for shielding (-)

23. Expansion Card Slots (cont’d)
USB ports often identified with a blue connector
Upgrading to USB 3.0
Install expansion card to PCIe slot
Install drivers
Accelerated Graphics Port (AGP) Designed exclusively for video card
Located close to RAM and CPU
DIME direct Memory Execute
Almost obsolete

24. Expansion Card Slots (cont’d)
By combining the functions of several separate technologies into one unit a more economical device can be produced:
AMR - Audio/Modem riser
ACR - Advanced Communication riser
CNR - Communication and Network riser
Combine NIC, modem, audio, USB and DSI cards

25. System Resources
Device Manager: Assigns and allocates system resources
Access device manager by typing “device manager” into search box
Lists hardware devices installed in system
Properties tab list information about hardware configuration and resources
Can view/update/roll back/uninstall drivers,

26. System Resources (cont’d)
Search System Information in search box
Select system summary
Operating system and version
Computer name
User name
Processor type
BIOS version
I/O Port and memory address
Memory address range: assigned section of memory used as temporary data storage
I/O Port address is assigned for identification

27. System Resources (cont’d)
Interrupt Request (IQR): literally interrupt as processes taking place in the CPU to give attention to some device such as the keyboard
IQR are numbered 0-15
Lower number = higher priority
Two IRQ assignments can be shared if devices are not used at same time (scanner and camera)
IF two devices with same IQR try to access CPU at same time system locks up
Hardware and software IQR exist

28. System Resources (cont’d)
Direct Memory Access (DMA) a combination of hardware and software that allows then hard drive to directly transfer data to memory without involving the CPU
DMA controller is a chip that controls the DMA channels
Bus Mastering takes control of the busses involved in DMA and allows devices to carryout tasks with without involving CPU

29. System Resources (cont’d)
Plug and Play: automatic assignments of system resources
Simply plug the device in and the computer configures it
Before Plug and Play techs needed to
Set jumpers
Set dip switches
Load drivers

30. Installing Software Drivers
Install drivers before installing hardware
Avoids O/S from selecting a generic driver which may not work
Drivers are usually supplied on a CD/DVD with the hardware
Device driver has rollback and update driver options
Motherboard chipsets also have drivers
Use custom install –choose exactly what software you want
Default install will load lots of extra/unwanted software

31. Upgrading BIOS
Upgrading BIOS common when upgrading hardware in older systems
To Upgrade BIOS
Older systems required new chip
EPROM: Remove foil label and shine ultraviolet light into hole under label to erase chip then reprogram
EEPROM (Flash BIOS) easily erased electronically then updated using software from the motherboard manufacturer’s website

32. Upgrading BIOS (cont’d)
General instructions for upgrading flash BIOS
Download new BIOS from website
Copy BIOS onto Flash drive
Boot PC with flash drive inserted
Run BIOS upgrade program
When asked, type exact name of BIOS file
IF asked if you want to backup existing BIOS – YES
When procedure is complete REBOOT PC
Enter setup utility and set it to its default settings
Save changes and REBOOT
During reboot enter SETUP and correct date/time/settings
Save changes and reboot one more time

33. Upgrading BIOS (cont’d)
Alternate BIOS upgrade (if equipped)
USB Flashback button found on back of motherboard
Insert USB flash drive with new BIOS into white USB 2.0
Press button
BI(OS firmware is automatically updated!

34. Setup Utility Setup utility allows you to Identify type of hard drive
Identify chipset
Set password for setup utility
Select power management features
Configure boot order
Setup utility is activated by a special set of keystrokes displayed during startup (or check motherboard manufacturer’s website)
Move jumper to “clear CMOS” and back to clear P/W*

35. Troubleshooting Motherboards
Motherboard manufacturer include drawings of motherboards with component locations in user guides and websites
Motherboard is one of the most expensive parts to replace
Trouble shooting may require third party diagnostic software or hardware
First trouble shoot failed hardware to ensure it is not the problem (i.e. modem not working)

36. Troubleshooting Motherboards
Check for loose connections unplug and plug connections and jumpers
Remove and reinstall the CPU
Check for signs of high voltage damage
If problem disappears when case is removed check for pinched cables
Check motherboard manufacturers website for information and procedures
After all methods of diagnostic have been exhausted motherboard must be changes to be sure

37. End of Chapter 3
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