A small or large circuit board inside a cabinet containing most of the electronic components.
Everything connected to the computer is directly or indirectly plugged into motherboard. Components like CPU, BIOS, ROM, RAM, chips, and CMOS setup information.
Expansion slots for installing different cards like video, sound, graphics, and NIC.
Also contains RAM slots, system chipset, controllers and underlying circuit to tie it together.
Types of Motherboard
Non-integrated:
Assemblies such as I/O port connectors, hard drive connectors, CD drive connectors etc installed as expansion boards.
Takes lot of free space inside the case because of expansion slots.
If something goes wrong such as bend or broken pin or defective controller can be repaired with minor cost.
Are cheap and easy to produce.
Most of the olden motherboards were non-integrated.
Integrated:
Assemblies are integrated or built right onto the board.
Serial and parallel ports, IDE, CD drive are directly connected to the motherboard.
This tends to free some space inside case and better accessibility to the components.
Cheaper to produce but are expensive to repair.
Fast, powerful, feature rich motherboard at reasonable price.
Motherboard form factors:
Determines general layout, size and feature placement on the motherboard.
Form factors such as physical size, shape, component placement, power supply connectors etc.
Various form factors of motherboards are AT, Baby AT, ATX, Mini-ATX, Micro-ATX, Flex ATX, LPX and Mini LPX and NLX.
1) AT (Advanced Technology):
Oldest and biggest form factor and popular until Baby AT.
Capable of using 386 processor.
12' inch size and was difficult to install, service and upgrade.
2) Baby AT:
Standard in computer industries and still being used in Pentium class products.
CPU socket is placed in such a way that it can interfere with longer bus cards.
Limitation over peripheral card installation.
I/O ports are connected to pin-outs near the floppy drive which results in jumbling of ribbon cables.
3) ATX (Advanced Technology Extended):
Improvement done in easy to use, support for current and future I/O, and also to current and future technology.
New mounting configuration for power supply.
Processor relocated away from expansion slots to allow full length add-in cards.
Provides air-flow through chassis and across the processor.
4) Mini ATX:
Commonly same as ATX.
Just change in size from ATX= 12" x 9.6" to Mini ATX= 11.2" x 8.2".
5) Micro ATX:
Supports current and new processor technologies.
AGP (Accelerated graphics port) to have high performance graphics.
Smaller in size and less power supply.
6) Flex ATX:
A subset of micro ATX.
Gives chance to system developers to create new personal computer design.
Enhanced flexibility to allow custom case and board design to be manufactured.
Small motherboard size and supports current processor technology.
7) LPX (Low Profile Extension) and Mini LPX:
Based on design by western digital.
Usually found in desktop pc's.
Case are slim-line, low profile case with riser card arrangement for expansion cards.
Riser card arrangement means expansion boards are parallel rather than perpendicular.
This make smaller case but limits number of expansion slots to two or three.
High quality product at low cost but makes difficult to upgrade and repair.
8) NLX (New Low Profile Extended):
Supports current and future processor technologies.