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• Why it is called “Motherboard”
– Acts as the main platform.
– Printed circuit board.
• Also known as
– Main board, system board, planar board and a Mobo.
• It holds
– Processor, memory & expansion slots.
• Made up of
– Chipset, some code in ROM and various
interconnections and buses.
• Motherboards are produced in a variety of
– Sizes and shapes
• Driver selection of
– Power supply, case, CPU, cards.
• Using a matching form factor assures you that:
– The motherboard fits in the case.
– The power supply cords provide the correct voltage, and
the connectors match the connections.
– Wires for switches and lights on the front of the case
match up with connections on the motherboard.
Types of form factor
Form Factor Motherboard Size () Description
ATX , Full size 12”x 9.6” Popular, Had many
MicroATX 9.6”x9.6” Smaller version of ATX
FlexATX 9”x7.5” Smaller version of
BTX 12.8” wide Improved over ATX, Up to 7
MicroBTX 10.4” wide Up to 4 Expansion slots
PicoBTX 8” wide No or one Expansion slot
NLX 9”x13.6” Used in low end system
ATX – Advanced Technology eXtended
• ATX is a specification used to
– Outline motherboard configuration and dimensions.
– Improve standardization.
• In 1996 replaced by Baby AT in new systems.
• ATX – 20pins provides +3.3v,+5v,+12v,-12v rarely
• ATX 2.2 – 24pins
• It has the COM port, LPT port, PS/2, and USB
mounted directly on the motherboard.
– BIOS program continually checks the CPU
temperature and voltages, the cooling fan’s RPM.
– If overheating occurs, PC will shutdown automatically.
– Relocation of the memory and the CPU allows for
better ventilation and easier installation.
– Power management is now possible with proper BIOS
BTX – Balanced Technology eXtended
• The BTX was designed for
– Flexibility, used by everything from large tower
systems to those ultra-small systems that sit under
– Takes full advantage of SATA, USB 2.0, and PCI
– Uses one or more auxiliary power connectors for
the processor, fans, and lighting inside the case.
• Can use an ATX power supply.
• 24 pin power connector.
– Focuses on reducing heat with better airflow.
– Improved fans and coolers.
– It also gives better structural support for the
motherboard than does ATX.
– Slow adoption rate from developers.
– Do not fit inside ATX cases and vice versa.
– Requires new case and power supplies.
• Clock generator
• CPU socket
• Memory socket memory error checking
• ROM BIOS
• CMOS RAM
• Expansion slot
• IDE ports
• Floppy disk port
• IO Connectors/ USB ports
• CMOS Battery
– Complementary Metal Oxide Semi-Conductor.
– A 3.0 Volts lithium type cell.
– The cell is responsible for storing the information in
– Basic Input Output System.
– In the form of a Chip.
– Contains all the information and settings of the
– Non volatile storage.
– Remembers its contents even when power turned off.
– Startup instructions are stored, called firmware.
• Expansion Slots
• Industry Standard Architecture(ISA) Slots
– Oldest slots in the history of motherboards.
– Conventional display cards or sound cards were
– A 16- bit bus.
• Peripheral Component Interconnect/PCI Slots
– Vastly used to install add-on cards .
– 64-bit high-speed bus.
• PCI express/PCIe Slots
– Latest and the fastest component.
– Supports add-on cards & full duplex serial bus.
• Accelerated graphics port(AGP) slot
– Used to install a latest graphics card.
– Runs on a 32-bit bus and both PCIe and AGP can
be used to install high-end gaming display cards.
• RAM(memory) slots
• Single In-line Memory Module (SIMM) slots.
– Found in older motherboards.
– The SIMM supports 32-bit bus.
• Double In-line Memory Module (DIMM) slots.
– Latest RAM slots which run on a faster 64-bit bus.
– The DIMM used on Laptop boards are called SO-
• CPU Socket
– An electronic component that attaches PCB and is
designed to house a CPU.
– Special type of IC socket designed for very high pin
• The CPU and RAM communication
– RAM contains data.
– CPU processes data.
– The data bus transports
processed data to the RAM
so it can be stored, displayed.
• Power Connectors
– Receives power from SMPS(Switched mode Power
• AT connector
– It consists of 2 number of 6 pin male connectors.
– Found on old types of motherboards.
• ATX connector
– They are either 20 or 24 pin female connectors.
– Found in all the latest types of motherboards.
• Integrated Drive Electronics (IDE) connectors
– Used to interface disk drives.
– The 40-pin male connector - IDE hard disk drives
– The 34-pin male connector - Floppy Disk Drive.
• Serial Advance Technology Attachment(SATA)
– 7-pin connectors to interface SATA hard disks.
– They are much faster than IDE interface.
– Helps the main processor in mathematical
calculations and computer graphics.
• Cabinet connections
– Has many buttons that connect to the
– Some of the common connectors are Power
Switch, Reset Switch, Front USB, Front Audio,
Power indicator(LED) and HDD LED.