What is Motherboard in a Computer?

If you open your computer, you will see a large circuit board on the bottom or side of a computer case, into which other circuit boards are plugged. This large circuit board is called motherboard.

A motherboard in a computer is a large rectangular circuit board that sits inside a computer case and controls the operations of all other components.

Sometimes, it is also known as a main board or system board. It is the main hardware component in any computer system that holds and connects together various essential components of a computer.

It usually accommodates a central processing unit (CPU), BIOS (Basic Input/Output System) memory chip, heat sink/fan assembly, RAM, expansion slots, chipset, sockets, internal and external connectors, and various ports. This board also contains embedded wires that interconnect motherboard components.

All the other circuit boards having chips or other electronic components are connected to a common circuit board called motherboard. Therefore, it is known as a mother of all other circuit boards.

A motherboard is a heart of any computer machine because it performs several important functions to the functioning of a computer. It provides electrical pathways and data transfer capabilities between the processor, memory, storage, expansion cards, and other peripheral devices.

A typical computer motherboard consists of chipsets, multiple slots, connectors, and sockets designed to accommodate specific hardware, as shown in the below figure.

Computer motherboard

For example, CPU sockets allow the installation of one or more processors, memory slots hold RAM modules, and expansion slots enable for the addition of expansion cards (such as graphics cards, sound cards, or network cards).

This main circuit board provides a common platform through which all the hardware components of a computer system communicate or interact with each other and perform necessary functions. The computer’s overall performance and functionality may be significantly impacted by its design, compatibility, and capabilities.

Computer Motherboard: A Brief History


There are three basic factors that generally affect all the computer motherboards. They are:

  • form factor: It determines the actual physical dimensions of the board.
  • chipset: It specifies what supporting chips will place on the board to control the flow of data.
  • bus: It specifies the actual design of the circuit traces on the board and the electrical signals that flow across the circuit traces.

In Aug 1981, IBM (International Business Management) had introduced the first motherboard named “planar” in the world. It had installed in the original personal computer (PC) to provide the basic of computing to the home user.


This PC’s motherboard had included an Intel processor chip, and 16 kilobytes of memory chip (expandable to 256 kilobytes). It had five expansion slots that were configured much like today’s ISA (Industry Standard Architecture) slots.

The bus structure could handle only 8 bits of information at a time. The back of the circuit board has two connectors, one for the connection of a keyboard, and second for the connection of a cassette tap.

In 1983, IBM released eXtended Technology computer with three additional expansion slots added to the motherboard. However, keyboard connectors became standard on all the later motherboards, and floppy drives replaced the cassette connector. The capability of primary memory RAM was increased to 640 KB and introduced the newly hard drives.

Finally, In 1984, IBM released the Advanced Technology (AT) form factor. This technology made the PC better than the previous. The AT used a 16-bit data paths, meaning that it allows to travel 16 bits of information across the motherboard at a time.

The ISA slots were converted to 16-bit slots. However, one or two slots had kept to an 8-bit configuration for backward compatibility with XT boards.

Types of Computer Motherboards


Motherboards of a computer come in different sizes, shapes, and features. Here are its major types:

  • eXtended Technology (XT)
  • Advanced Technology (AT)
  • Standard ATX
  • Micro ATX
  • Mini-ITX
  • Mini STX
  • extended ATX (EATX)

Let us understand each motherboard and its characteristics in brief.


XT Motherboard

In 1983, IBM introduced XT (eXtended Technology) motherboard that was used to upgrade the original personal computer (PC). It played a significant role in the early development of personal computing.

The XT motherboard had a rectangular shape and measured approximately 8.5 x 11 inches (216 x 279 mm). This form factor became the standard for early desktop computers.


On this motherboard, there was a processor socket to accommodate 8-bit Intel 8088 processor, enabling data transfer and control between various components. This motherboard typically had 5 to 8 ISA (Industry Standard Architecture) expansion slots, memory slots, BIOS, and connectors..

Expansion slots allowed the users to add additional expansion cards, such as graphics, sound, and networking cards, to enhance the system’s capabilities. XT motherboard supported a maximum of 640 KB of RAM using 16-pin DIP (Dual In-Line Package) memory chips in the memory slots.

This motherboard had utilized a Basic Input/Output System (BIOS) chip that controlled the initialization process during startup and provided low-level hardware interaction instructions.

XT motherboard also contained various connectors for peripheral devices, such as serial and parallel ports, keyboard and mouse ports, and floppy disk drive connectors. These connectors allowed users to connect external devices to the system.


Advanced Technology (AT) motherboard

In 1984, IBM introduced advanced technology (AT) motherboard as an advancement over its predecessor, the XT motherboard. It was widely used at that time. It had a standardized form factor and connectivity of various components.

The form factor of AT motherboard was approximately 12 * 13.8 inches (305 * 350 mm). This larger size was essential to accommodate the components and connectors available at that time.

It accommodated a 16-bit Intel 80286 processor socket, BIOS chip, a unique 5-pin DIN keyboard connector, and two-piece power supply connector. AT motherboard typically had 30-pin SIMM (Single In-Line Memory Module) memory slots for the installation of RAM, and 16-bit ISA standard expansion slots.


Standard ATX Motherboards

In 1995, Intel introduced ATX (Advanced Technology eXtended) motherboard that is an enhanced version of AT motherboard. This motherboard revolutionized the industry with its improved design, expandability, and ease to use. It is the most common type of motherboards found in the desktop computers.

The ATX motherboard is 2 x 9.6 inches (305 x 244 mm), and has COM port, LPT port, PS/2, and USB mounted directly on the motherboard. It included advanced BIOS chip that continuously checks the CPU temperature, voltages, cooling fans RPM, etc. If the processor over heats, the PC shuts down automatically.

Power supply was positioned at the top of the previous designed motherboard, while ATX motherboards placed the power supply at the back of the case. This arrangement improved cooling and cable management.

ATX motherboards has a inbuilt I/O (Input/Output) shield on the back panel. This shield includes ports for USB, audio, Ethernet, and other peripheral devices, simplifying the installation process.

They typically introduced several expansion slots, including PCIe (Peripheral Component Interconnect Express) slots for graphics cards and other high-speed peripheral devices.

ATX motherboards included multiple RAM slots that allow us to increase memory capacity and faster data access. They also featured multiple SATA (Serial Advanced Technology Attachment) ports for connecting storage drives.


Micro ATX Motherboards

In December 1997, Intel first introduced micro ATX motherboard, that is a smaller version of the ATX motherboard. It is designed to fit into smaller computer cases or ATX cases.

MicroATX motherboard is a 9.6 x 9.6 inches (244 x 244 mm), that makes it more compact than standard ATX motherboard. It is suitable for smaller computer cases where space is a constraint.

MicroATX motherboards are designed with fewer expansion slots compared to standard ATX motherboards. They contain multiple RAM slots to increase the memory capacity so that users can perform multitasking smoothly. In terms of storage, they usually provide several SATA (Serial Advanced Technology Attachment) ports for connecting hard drives and SSDs.

Micro ATX come with various connectivity, including USB ports, audio jacks, ethernet ports, and video outputs. While, the number of ports may vary depending on the specific model. They generally provide ample options for connecting peripherals and external devices.


Mini ITX Motherboards

In 2000, Intel first introduced mini ATX motherboard, that is a smaller version of the micro ATX motherboard. This motherboard is a merely 6.7 x 6.7 inches (170 x 170 mm), that makes it significantly smaller than Micro ATX and ATX. This compact size enables to design of an ultra-small PCs.

Two RAM slots for a maximum memory capacity of 32 GB or more, and multiple SATA (Serial Advanced Technology Attachment) ports for connecting hard drives and SSDs are mounted on mini ITX motherboard. This motherboard also contains several connectivity options, including USB ports, audio jacks, ethernet ports, and video outputs.


Mini STX Motherboard

In 2015, Intel introduced a Mini STX (Mini Socket Technology eXtended) motherboard which is in rectangular shape, having a dimension of 5.8 * 5.5 inches (147 mm * 147 mm). Due to its compact size, it is significantly smaller as compared to Micro ATX, and even Mini ITX motherboards.

This motherboard has a unique Mini STX socket to support powerful processors, such as Intel Core i7 and i5 CPUs. This feature makes it suitable for tasks such as gaming, multimedia editing, and office productivity.

Mini STX motherboard contains memory slots for DDR4 RAM modules, enabling users to take advantage of the latest memory technology. It also support SSDs, which provides high-speed data transfer rates and ample storage capacity.

Mini-STX provides many connectivity, such as USB ports, ethernet ports for networking, audio jack, HDMI port for video, and PCIe expansion slots to add dedicated graphics cards, sound cards, or other expansion cards.


eXtended ATX Motherboard

An eXtended ATX motherboard is a larger variant of the standard ATX motherboard whose dimensions are 344 millimeters by 330 millimeters (dimensions will differ with different manufacturers). This motherboard provides additional space and features to accommodate more expansion slots, connectors, and components. It supports a single or a twin CPU configuration and has up to eight RAM slots.

In addition, it has a higher number of PCIe (where e is for Express) and PCI slots, which may be used to add PCI cards for a wide range of applications such as gaming, video editing software, etc.

The eXtended ATX motherboards incorporate robust power delivery systems with multiple power phases, high-quality capacitors, and voltage regulation modules. It supply the stable power to the CPU and other components that reduces the risk of system instability and improve overall performance.


In this tutorial, we have discussed what is motherboard in a computer and its various types. Hope that you will have understood the basic points of computer motherboard and enjoyed this tutorial. In the next, we will get the complete knowledge of components of motherboard and their functions of a computer system.
Thanks for reading!!!

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