Parts of Motherboard and its Function Explained

👤 Diwas Poudel    🕒 Sep 2 2021    📁 Fix    📜 0 comment

Before discussing various parts of the motherboard. Let's discuss some basic terminology so that we can be familiar with the content. What is a computer? The computer is an electronic device that accepts raw data, processes it, and produces an output. All the devices that we see on the computer are directly or indirectly connected to the motherboard. So, people generally called the motherboard the backbone or spine of the computer. The motherboard is present in every electronic device from tablets, smartphones, PCs, etc and its sizes vary according to the devices.

What is a Motherboard?

The motherboard is a thin printed circuit board (PCB) which links all different components inside your computer. So, we can say the motherboard acts as a hub in a network. People call motherboard with a different name like mainboard, logic board, baseboard, system board, mobo, etc.

Location of Motherboard:

In Desktop PC: In a desktop PC, you will find a big rectangular computer case. Once you open the case to expose it inside the machine, you will find green/blue/brown/red large square printed circuit plate. This plate is the motherboard of the PC.

In laptop: If you open the bottom cover of your laptop, you will get exposed to the large PCB board which is the motherboard.

In smartphone: When you open the back cover of the smartphone, and screws up some pins then you will find your motherboard.

Types of Motherboard 

In all the programmable electronics devices motherboard is a large PCB board. The component attached to the board may vary from system to system. The desktop has different kinds of sockets and hardware which may vary from a smartphone. General components like CPU, memory, storage, capacitor, transistor, slots, connectors are
common in all electronic devices.

If you know all of these components on the desktop, then you can easily get an idea about components in other electronic devices. So in this article, we focus on desktop components.

Parts of Motherboard

important parts of motherboard

Parts of the Motherboard are as follow.

  • RAM Chip and RAM Slot
  • CPU Chip and Socket
  • PCI Slots
  • ROM Chip
  • Accelerated Graphics Port 
  • North Bridge
  • SouthBridge
  • CMOS Battery
  • Power Supply Plug
  • Parallel Port
  • Serial Port
  • SATA and PATA Connector
  • USB Port
  • DVI Port
  • RJ-45 Port
  • HDMI Port
  • FDD Connector
  • Optical Drive Audio Connector
  • 1394 Headers
  • F Audio Connectors
  • Heat Sink
  • Switches and Jumper
  • Microphone port, headphone port, subwoofer port, guitar port, DVD player port, stereo receiver port
  • Capacitor
  • Transistor
  • VRMs
  • Mounting Screw Hole
  • Power, Reset, SW, LED Pins
Also Read: Laptop Ports explained in depth

Now let's understand each of them.

1) RAM chip and RAM Slot

RAM stands for  Random Access Memory. It is also called the main memory.RAM is a temporary data storage device in computers and other devices. Data stored in RAM will get erased as soon as power is turned off. 

In layman's terms, RAM is analogous to short term memory.RAM forgets its content as soon as power is off, the Information store in short-term memory will get lost after a few days.

RAM has bidirectional data transfer capacity from CPU to memory during a write operation and from RAM to CPU during the reading operation. It acts as a mediator for data transfer from CPU to other devices like HDD, cdrom, PEN drives.

It is called Random-access memory because any memory address of RAM can be accessed directly from any location. If row number and column number are known then data in any memory location can be accessed.

Various types of RAM are available in the market some of them are DRAM, SDRAM, DDR, SRAM, CMOS RAM,VRAM etc. Generally available RAM in the PC market is from 2 GB to 16 GB.


Also Read: Understand RAM in depth


ram chip and slot

2) CPU Chip and Socket

CPU stands for Central Processing Unit. Considered the brain of the computer and other electronic devices because all the decision-making tasks of the computer are performed by the CPU. It is a large printed circuit board where all the components and peripherals are directly or indirectly connected. The main function of the CPU is to execute basics arithmetical, logical, and input/output operations.

cpu chip and cpu socket

CPU consists of 3 main typical components. ALU, CU
ALU: Arithmetical Logical Unit (ALU) is a digital circuit(gates) of CPU which is used for performing all arithmetical and logical operations. Some normal arithmetical operations performed by ALU are addition, subtraction, multiplication, and division. Some logical operations performed by ALU is comparisons between numbers and letters. A single CPU may also contain more than one ALU.

CU: Control Unit (CU) is a digital circuit of CPU which controls all the operations within the CPU.It allows and teaches various logical units, I/O devices, the memory of the computer how to respond to a program's instructions of the various components as well as the user.

Memory or Storage Unit:

3) PCI Slots and PCI Chip

Peripheral Component Interconnected(PCI) is an attached hardware component of motherboard for connecting various hardware components like modems, disk controller, NIC cards, Sound Card, graphics cards, SSD add-on cards, RAID cards, extra USB and serial port required so PCI slots help increasing motherboard capabilities without adding or replacing the motherboard.

If you have limited ports and slots on the motherboard to connects various types of hardware devices like saying graphics card port(AGP port) then you can use PCI slots to connects Graphics cards and enjoy the same features. Same way if you have a limited USB port in your computer system and want more then you can use a USB expansion card and get more USB ports in your system.

It was introduced in 1992, before that ISA, EISA was used for the same purpose. Later in 2004 PCIe slot is developed and it is replacing PCI slots, AGP slots, and ISA slots.

Also Read: PCI slots, PCIe Slots, function, types in Detail

Showing PCI slots, AGP slots, and ISA slots in the same picture:

General FAQs

1. What is the full form of PCI  and PCIe(or PCI-E)?

Ans: PCI stands for Peripheral Component Interconnected. PCIe stands for Peripheral Component Interconnected Express.

2. Do we have PCI slots on laptops?

Ans: Generally PCI slots are available on desktop PC but not in most laptops do not have reusable PCI slots because of their compact size and space. On some laptops, we can use it if you have ExpressCard Slots and can get adaptors to use PCI or PCIe.

3. Check which version of the PCI slot installed on the computer?

Ans: There are manual ways by going into the device manager. Better try using CPU-Z software for getting a detailed view of all versions of installed hardware. 

4) ROM Chip

ROM is nonvolatile storage whose content will not get erased even after power is cut off. Content stored in ROM is impossible or very difficult to modify.ROM contains only a few KB of information where all the BIOS information is stored, it tells how to starts, what to do when starts, which driver to load, CPU fan speed information, boot sequences information, system date time, etc.


5) AGP Slot and Chip

Accelerated Graphics Port Slot( AGP Slot) is a kind of expansion slot like a PCI slot but mainly designed for graphics cards. It was first introduced by Intel in 1996. We can easily locate this expansion slot because it is usually presented in brown color.

Also read: CPU hyperthreading in depth

6) North Bridge

North Bridge is also called Host bridge or Memory Controller Hub. It acts as the primary controller in the motherboard which directs traffics to and from the CPU.So, the performance of the computer also depends on the northbridge chip. It does lots of processing so it generally comes with a heatsink.

Characteristics of North Bridge:

  • It connects southbridge to the CPU.
  • It handles and communicates faster components on the motherboard like Main Memory, AGP, PCIe, ROM, and CPU.
  • It acts as a controller in bus speed on the motherboard.
  • Generally, it does lots of work with the CPU, so it is located near to the CPU generally with the heatsink.
  • It is a core component and is directly connected to the CPU.

In some processors of Intel, all the functioning of northbridge is performed by the CPU.


7) South Bridge

Southbridge is an IC chip that generally handles and controls IO functioning in the motherboard. Unlike Northbridge, it does not have direct with CPU. It generally handles low-speed devices because its communication speed is lower. Instruction from CPU reaches northbridge then from northbridge to southbridge. It is connected to the PCI bus, ISA buses, IDE buses, audio, serial devices like mouse, keyboard, USB ports, etc, and SATA hard disk connector.

In size, it is smaller than the northbridge. And in some southbridge, we can find heatsink attached to it.

Also Read: Why Windows OS is popular than Linux and macOS?

8) CMOS Backup Battery

CMOS stands for "Complementary Metal Oxide Semiconductor" and found in both laptop and desktop PC as a small circular coin shape.CMOS stores a wide range of system information like current system clock, date, time, pulses, mostly used hardware settings, BIOS configuration settings, BOOT sequences, BIOS master/admin password, GPU, and virtualization settings, power management, etc. They can save those set for a longer time around 2 to 10 years.CMOS works continuously even if you shut down your system because it is continually holding all those setting mention above.

CMOS battery looks like this:

cmos battery and its location

CMOS is also called CMOS RAM, COS-MOS, NVRAM(Non-Volatile RAM) in the market.

It is also called the RTC(Real Time Clock) of the computer system because even computer is shut down it is able to store all the required information that the system required to boot the system next time.

More About CMOS
1) CMOS chips were first introduced in the IBM computer.
2) CMOS is low-power technology chips so it lasts longer.
3) CMOS can store usually up to 256 bytes of information.
4) CMOS battery in laptop and desktop PC is 3V 
5) CMOS battery life lasts 2 to 10 years (source: hp store)
6) Commonly used CMOS battery in PCs is CR2032 lithium coin cell 


 Q1) What happens if the CMOS battery Dies?

Ans: CMOS battery in PCs operates at 3V.If the CMOS battery goes below 2.6V then CMOS has more chances to lose BIOS Settings and hardware setting, date, and times. Even sometimes the Operating System will also not load.

9)Power Supply Plug

The main work of the Power Supply port in the Motherboard is to provide power to Motherboard and its attached components and peripherals.

i) 24 (20 + 4) ATX power supply
In modern PCs, ATX power supply is provided which is 24 Pin(20 + 4) Main Power Supply Connector (Older Pcs only have 20 Pin)

ii) 4 Pin or 8 Pin Connector
This port in the motherboard is to provide dedicated power to the CPU. Older PCs may not have this Plugin motherboard but modern computers can do lots of works like overclocking so, a dedicated cable is provided to the CPU.

8Pin connector can be split into two and each split part can be used as a 4 pin connector.

iii) PCI-Express 6-Pin or 8-Pin Connector
This is required to power the PCI-E port.PCI-E slot required 75W power to operates.

THE older PC does not have this.

iv) Molex
Molex pin is 4 power pin which is required to supply power to older CDROM and hard drives. Molex is nowadays used for Case Fan. (some have some do not have)

Molex connector comes with Mini Molex connectors, which is used for floppy disk drives in much older PCs.

v) SATA power supply
Modern hard drives and CDROM uses SATA cable for power. In the motherboard, it is an L-shape port and so its cable is connected to the SATA port in one way only. In motherboard, it has 15 pins. It provides features of hot-swappable hard drives ie. plug and play hard drive features.

10) SATA and PATA Port and Connector

PATA stands for Parallel Advanced Technology Attachment. It is 40 pins long and wide ribbon cable used for connecting mass storage devices like hard disks(HDD or SSD), optical drives to the computer. It was launched in 1986 by Western Digital and Compaq. Every cable of PATA has two or three connectors, of which one is attached to the adapter interfacing and the remaining are plugged into secondary storage devices.

In modern computers, it is not used. It is outdated technology and is replaced by SATA Technology

SATA stands for Serial Advanced Technology Attachment. It is a 7 pin cable which is shorter and powerful than the PATA connector and its function is the same as the PATA connector. The first version of SATA was launched in 2000.


There are several advantages of using SATA over PATA

  • Reduce Cable Size: The size of the SATA cable is shorter than the PATA cable.The maximum cable length of SATA cable is 18 inch and PATA maximum cable length is ~ 39 inches.
  • Higher Bandwidth: The bandwidth ranges of various PATA cable is between 16 MB/s - 133 MB/s. But bandwidth ranges of various SATA cable is between 150 MB/s - 600 MB/s.
  • SATA has hot-swappable features: SATA cable from the devices can be plugged in and out even system is ON(But don't try with running hard disk or CDROM). Hot-swappable does not work with PATA.  Try it(Remove SATA cable from CDROM, Restart your PC then insert SATA in CDROM, it will work.)

      Try it (Remove PATA cable from CDROM, Restart your PC then insert PATA in CDROM, it will not work. Precaution: Don't do this hot-swap with PATA cable).

  • SATA cable is cheaper than PATA cable.
  • SATA offers an external interface but PATA doesn't.

11) Parallel Port

A parallel port is used to transfer in a parallel manner through multiple communication channels. Used for printers, scanner, Zip Drive, external HDD, tape backup devices, external CD ROM, etc.

parallel port

Click here for how parallel port from external looks like.

12) Serial Port

With a serial port, only one bit of data gets transfer at a time. It is found in an older PC to connect older keyboards, PDAs, external modems.

serial port and pin

13) PS/2 Port

PS/2 port was popular in older desktop PCs.But now it is obsolete.

  • PS/2 (green color ) is for the mouse.
  • PS/2 (purple) is for the keyboard.

frontpanel motherboard

14) USB Port

USB stands for Universal Serial Bus. Its transfer rates are faster than the PS/2 connector so modern PC we don't find a PS/2 port. There are various types of USB port some of them are :

  • Type A
  • Type B
  • Type C
  • Type A Mini
  • Type B Mini
  • Type A Micro
  • Type B Micro
  • Type B Micro USB3
Also Read:  Learn about USB port in depth

15) RJ-45 Port

RJ stands for Register Jack. It looks like a telephone jack but slightly bigger.RJ45 is also called Ethernet Port because it is used to provide the internet to the computer.RJ 45 port is used to connect to Local Area Network using a twisted pair ethernet cable. Ethernet Cable has a connector this connector is connected to the RJ45 port.

16) HDMI port

HDMI stands for High Definition Multimedia Interface. It was developed in 2002 AD. It looks like a USB port but it is quite larger in size.HDMI is a digital interface for transmission of audio and video data in a single cable to digital devices like digital TV, projector, gaming console, computer, mobile devices, digital camera, cable box, blu ray, etc.

About HDMI port types visit the below link;

Also Read: About HDMI Types

17) Audio Port

Most of the desktop computer nowadays comes with 3 to 6 port.

  • Green Color Port is a Line Out which is for headphones and stereo speakers.
  • Pink /Light Pink Port for Microphones input.
  • Light Blue Port is line In which is for mp3 players, DVD player, CD player, stereo receiver, turntable, electric guitar, VCR audio outputs.
  • Dolby Audio Black Port for rear speaker.
  • Orange/yellow port is Center/Bass Channel which is for subwoofer


18)  Heatsink 

Heatsinks use a thermal conductor to reduce heat generated and prevent overheating from hardware components like CPU, GPU, northbridge, southbridge, RAM modules, etc. In general, that component that generates heats required a heatsink.

CPU has to perform a large number of tasks every second. While performing large tasks, it beings to generate heat and if heat is not maintained then
the processor will destroy itself. Also at the top of the heatsink will have a FAN and this FAN helps to cool down the heat sink. This is Air coolant Heatsink

But in the market, we will have liquid coolant heatsink as well generally used in a high-end gaming environment, servers, and datacenter.

cpu heatsink , northbridge heatsink

19) Switches and Jumper

Switches and jumpers are used to reconfigure the circuit onto an existing circuit board in a reversible way.

Jumper also called Jumper Shunt is a small circuit board used to close, open or bypass part of an electronic circuit.

Closed Stage Jumper: If the plug is pushed down over two pins, the jumper is referred to as jumpered.

Opened Stage Jumper: If there is no plug into the pin then it is an open stage.


🔥 Caution: Before adjusting jumper configuration make sure that the system is turned off otherwise system may get damaged.

20) Capacitor

A capacitor is an electronic device used for filtering, decoupling, and timing the circuit in the motherboard. There are more capacitors in the motherboard which mostly does decoupling functionality, so those capacitors are called a decoupling capacitor. A decoupling capacitor is used for stabilizing power in each IC used in the system.

It comes with various voltage levels like 3.3 V, 5 V, 12 V.


Suppose a circuit needs 5 V input than before that circuit there will be capacitors in parallel which allow up to 5 V to pass to that circuit.

21) Transistor and MOSFET

Transistor is used in most of the component of motherboard for various purpose like

  • controlling the amount of current or voltage in the component
  • amplification/modulation electronic signal
  • switching of an electronic signal and electrical power.

Today's motherboard has SMD(Surface Mount Device) transistor which uses Surface Mount Technology(SMT). They are found mounted in the motherboard.

MOSFET(Metal Oxide Semiconductor Field Effect Transistor) is the most widely used transistor in motherboards.

Denoting letter for Mosfet and Transistor is same: ie. Q, PQ

22) Diode

Motherboard in your laptop, mobile phone has SMD Diode and they are mounted in your motherboard.

The main function of the diode is to allow the current flow in one direction like a one-way street. It helps to converts voltage spikes in the motherboard by converting spikes alternating current(AC) voltage to direct current.

Denoting letter for Diode : D

23) VRMs

VRMs stands for Voltage Regulator module.VRMs are electronic circuits located near the CPU and their main works are to provide steady and consistent voltage to the processor. As Powersupply unit converts external voltage eg. 240 volts to 12V or 5 V, this voltage is again taken by VRMs first and then again step down and regulates these voltages and provide the continuous required power to the processor.

It is especially important for overclocking a CPU or GPU.


24) Mounting Screw Hole

Mounting holes let us mount our motherboard to a surface.

You simply have to pick a screw size that matches the size of mounting holes in your motherboard, find a surface to which it will be mounted and drill accordingly.