What Is A Computer Motherboard?

There’s a specific kind of computer component that I end up having to work with a lot when building a new computer, replacing parts, or doing general maintenance and cleaning. It’s one of the most critical pieces of a computer and to some, the most intimidating piece as well. I can’t be referring to anything else other than the motherboard. It’s something I always like to learn more about in my spare time, as it’s one of the most complicated pieces of equipment I work with on a day to day bases. To that end, I wanted to share some of the knowledge I’ve acquired over the years.

So what is a computer motherboard? A computer motherboard is the primary circuit board found inside a computer case. It houses many of the critical computer components like the computer processor and RAM. It also allows for the communication between the entire computer itself. A motherboard is typically made of a firm printed sheet of non-conductive material mixed with thin layers of copper or aluminum foil that form the electrical circuitry between the components.


There’s definitely a lot more to what a motherboard actually is than a single definition though, and I’d like to go into more detail below!

 

Important Terms to Know About Computer Motherboards

Before we really dive into motherboards head first, there’s some important terms we need to go over first. Because the motherboard is the interconnecting critical component of most of your computer, there are a lot of things you’ll potentially need to know. If you’re planning to buy a new board, understanding a lot of these terms will prove to be especially useful.

  • Form Factor – This is a shorthand term for the measured dimensions of a motherboard and the layout of it.
  • Mini-ITX – Designates a motherboard size measuring 6.75 x 6.75 inches. These are the smallest motherboards available for a personal computer.
  • MicroATX – Designates a motherboard size measuring 9.63 x 9.63 inches. These are not much bigger than mini-ITX boards but offer more flexibility.
  • ATX – Designates a motherboard size measuring 12 x 9.63 inches. This is the standard motherboard size and fits the needs of the large majority of computers.
  • E-ATX – Designates a motherboard size measuring 12 x 12 inches. This is a very large motherboard and is generally suited towards very expansion oriented rigs and only fits in full tower cases.
  • BIOS – Short for Basic Input/Output System. A dedicated chip on your motherboard that is standard firmware. It manages the crucial system settings like boot order and integrated components.
  • UEFI – Short for Unified Extensible Firmware Interface. This is a modern upgrade to the BIOS chip. It’s slowly becoming the industry standard and provides a much more user-friendly experience.
  • I/O Shield – This is the rectangular metal plate that covers the motherboard ports on the back of the computer. Sometimes called a back plate, I/O shields are cut specifically to match a single motherboard model and aren’t interchangeable.
  • Chipset – Defines a set of motherboard families that support a specific computer processor model. Manufacturers will usually produce various motherboards of different form factors that support a single processor model.
  • CPU Socket – This is the square port on the motherboard where the computer processor is fitted and secured. Ensure that you know what socket types your motherboard supports before buying a processor as they have to match.
  • DIMM – Short for Dual In-Line Memory Module. This is a set of two, four, or eight slots where you fit RAM.
  • RAM – Short for Random Access Memory. RAM holds frequently used data temporarily as you run your computer to speed up the access of that data later. When you shut down your computer, the temporary data is wiped clean.
  • DDR – Short for Dual Data Rate. This designates the speed at which two RAM sticks of the same model can work in unison. DDR speed is designated by a number following the acronym. DDR4 is the most common dual rate used in the modern era, but DDR3 can still be found in older motherboards.
  • PCI-E Slots – Short for PCI-Express Slots. These are expansion slots on the motherboard designated for graphics cards, TV tuners, wireless cards, and other expansion cards. Each motherboard will come with a set of PCI-E slots designated by an ‘X’. These slots are x16, x8, x4, and x1. The higher the number the longer the slot. Expansion cards will be labeled with what slot length they require.
  • USB Header – Short for Universal Serial Bus Header. These are pin headers on your motherboard that will connect to the USB ports located on the front of your computer case.
  • Front-Panel Header – Another set of pin headers on your motherboard that will connect multiple cables from your computer case. A front-panel header will typically cover the case’s power switch, reset switch, hard drive activity LED and power LED.
  • SATA Ports – Short for Serial ATA Ports. These are connection ports for hard disk drives (HDD), optical drives, and solid state drives (SSD).
  • 24-Pin ATX Power Connector – This is a connection port that the largest pin connector from the power supply unit plugs into. This powers the motherboard and has to be connected for the PC to operate.
  • +12V CPU Power Connector – A dedicated 4 pin or 8 pin header on the motherboard positioned near the CPU socket. A power supply cable will plug in here to power the processor.
  • PWM Fan Header – A number of 4 pin headers that are dedicated to powering computer case fans. These headers allow for more flexible control over fan settings that simply connecting them to the power supply.
  • CMOS – Short for Complementary Metal-Oxide-Semiconductor. This is an isolated chunk of memory that operates the BIOS and maintaining the system clock.
  • CMOS Battery – This is an on board battery that keeps the CMOS supplied with power even while the computer is turned off. Modern PCs usually operate with a CR2032 coin cell battery.
  • Debug LED – This is usually included on premium motherboards and offers a two digit LED readout. This readout corresponds to error codes that may be causing errors on the motherboard or preventing a computer to boot. The motherboard’s manual will have a list of these error codes that allow you to figure out hat the issue is exactly.

This was a big list, but a lot of this is important information. Even if it’s not always used in conversation about motherboards, understanding these terms is really critical to knowing what you’re reading about, especially when looking to purchase a motherboard!

A Closer Look at Motherboards

In some ways, a motherboard is a lot like a computer case. It holds a lot of components, but unlike a computer case, it does a bit more than that. A case has a few parts of its own that need to be powered, but generally its only true job is to hold everything together and look somewhat pleasing to the eye as well.

A motherboard however, is a very complex printed circuit board. Also, sometimes called mobos, MBs, main circuit board, system board, and mboard, motherboards are rarely pleasing to the eye like a computer case. They can’t afford to look good, as every little bit of space on a motherboard is instead needed to create complex designs of electrical traces that ensure that all the individual components of a motherboard, and the other components that it houses like the CPU, RAM, and graphics card, all communicate with each other smoothly.

Note: Because a motherboard consists of many complex arrays of electrical traces running through it, it isn’t in any way designed to be user serviceable. If your motherboard has issues, it is highly advised to take it to a professional and to not attempt repairs yourself!

A motherboard will always have basic features regardless of what manufacturer creates them. They will all have a CPU socket, RAM slots, PCI-E slots, and I/O ports. None of this will change unless the way a computer functions is completely reworked. They’re also standardized into specific form factors. These form factors are used by the industry to ensure that customers are able to easily identify which motherboard will fit in specific computer tower sizes.

I’ll leave a graph below to better show motherboard and computer case support:

Case Size and Motherboard Support Mini-ITX Motherboard Micro ATX Motherboard ATX Motherboard E-ATX Motherboard
SFF Case Yes No No No
Mini-Tower Yes Yes No No
Mid-Tower Yes Yes Yes No
Full Tower Yes Yes Yes Yes

If you’d like to learn more about what these computer tower sizes mean, I wrote another article all about them here. For motherboards though, the simple take away is that the larger the case, the more compatibility there is with board sizes.

As stated before, regardless of what size or brand motherboard you buy, it will come with certain essentials. That being said, the size of a motherboard can definitely influence how many of those essentials you get. A mini-ITX board for example, may only come with only two DIMM (Where the RAM goes) slots. An E-ATX on the other hand can have up to eight DIMM slots.

Similarly, motherboard size can dictate how many PCI-E slots you have. This is where you will be installing expansion cards and graphics cards. I’ll get more into these later in the article, but for now know that if you intend to put a high end graphics card in your system, you’ll want to skip mini-ITX. A lot of times these motherboards (and the cases they’re put in) just aren’t big enough for a full sized high end card.

Other things that a motherboard will come with regardless of the make and model are:

  • USB headers
  • Font-panel headers
  • PWM fan headers
  • SATA ports
  • 24 pin power connectors
  • A +12V CPU power connector
  • CMOS
  • A CMOS battery

A lot of this might sound like jargon, but really most of these are simply pin based connector or ports where you connect a cable of some kind to the motherboard. Every motherboard comes with a manual labeling every single header and connector and even if you lost it, the motherboard itself has all these labeled right next to the pins!

One thing that does not always come with a motherboard, and something I would highly recommend you check for of you plan on building a system, is a motherboard with a debug LED. This is a display module typically located on the bottom edge of the board. If your computer fails to boot (start up), this LED display will give you a two digit readout. You can then check your manual to find this readout and it will give you an exact explanation of the issue your motherboard is encountering.

This can save you hours of guesswork and headaches when trying to troubleshoot your system and I can’t recommend this one particular feature enough. Check and double check any board you intend to buy and be sure that it has this debug LED!

Finally, a quick word about BIOS and UEFI. These are separate and dedicated chips on your motherboard that contains firmware. This firmware is the set of data parameters that your motherboard operates from and while it can be tinkered with in the BIOS menu before your computer fully boots, it’s not recommended unless you’ve fully read up on what you’re doing.

UEFI is a modern successor to the BIOS, a firmware that has been around since 1975. BIOS has shown its age for a while now, and UEFI aims to address those shortcomings. In a sense, it still performs the same function, but offers a far more user-friendly interface. Most modern generation motherboards come with a UEFI dedicated chip and it’s highly recommended to use these newer boards for new system builds.

 

Motherboard Chipsets and CPU Sockets. What it All Means

A big elephant in the room when it comes to motherboards is the fact that a lot of people don’t know what chipsets and CPU sockets are. This isn’t surprising, and it’s nothing to feel frustrated by, as they can be a little confusing. I wanted to use an entire section of this article to break them both down and make them easier to understand.

Chipsets themselves is a blanket term for the electrical pathways on a motherboard that connect and control the rest of the computer with the power of the CPU. This means that, whenever a new high end computer processor is debuted to the public, it’s typically done in tandem with new motherboard chipsets being released to support these processors.

Whether it’s an Intel or AMD processor, manufacturers will fabricate a host of new boards to support them. All of these boards, if for example were made to support a new Intel processor, would offer the same chipset but would come in different form factors and offer a variety of different features. This is what is called a board family.

Having a board family allows for customers to pick out a motherboard that best suits their needs, while still knowing that the board they purchase, will support that computer processor.

At least, that’s the simple part of it. CPU sockets are where things start to get more complicated. This is the receptacle where you install the computer processor. Processors have different socket types that need to be matched with corresponding socket type on a motherboard.

This is complicated further by the fact that not all processors that use that specific socket type will necessarily work with a motherboard that supports that socket. Crazy, right?

What this boils down to is that if you intend to build a new computer, decide on a CPU first then search for a motherboard. And when you’re searching for a board, do research and check the board specs! Check multiple sites and sources and make absolutely sure that the CPU you have in mind will work with the socket type on the motherboard.

I cannot possible list every single socket type you may come across on this single article, however I’ll list the most common ones that you’ll likely encounter while searching for:

  • Socket 2011 and Socket 2066 – I’m including these two together because they look extremely similar to one another. The 2011 typically supports Intel i7 CPUs and 2066 typically support i9 CPUs. However, each socket type has different versions that are not compatible with one another. Check your motherboard specs before you buy!
  • Socket 1151 – Currently supports the latest Celeron, Pentium, and Core processors by Intel. It’s the successor to the 1150 socket type and just like the 2011 and 2066 it has different chipset versions that are incompatible. Check your motherboard specs before you buy!
  • AMD AM4 – This is the latest APU chipset that supports the AMD Ryzen CPUs. AMD has gone to greater lengths with the AM4 to make it more streamlined with compatibility, however there are still different chipset versions. Check your motherboard specs before you buy!
  • AMD TR4 – This is an absolutely massive socket type for AMD Ryzen Threadripper CPU series. It requires a special loading mechanism. You will likely not ever be using this socket type but it’s worth mentioning it anyway. As always, check your motherboard specs before you buy!
  • AMD FM2 and FM2+ – These socket types support AMD’s “accelerated processing units” (APUs) which is AMD’s attempt at a computer processor with video acceleration. These socket types are still around but not supported by newer motherboards. Check your motherboard specs before you buy!
  • AMD AM3+ – This socket type supported the final wave of AMD’s FX-series processors. Like the FM2, this socket type is still around but not supported by newer motherboards. Check your motherboard specs before you buy!

There will be new CPUs and motherboard chipsets to support them as the years roll on. I will do my best to keep this above list up to date as well as things change. As I stated many times though, and I cannot emphasize it enough, please check the specs of any motherboards you intend to buy and make absolutely sure they work with the CPU you’re interested in!

Motherboard PCI-E Slots

PCI-E is short for Peripheral Component Interconnect Express. These are slots on your motherboard that allow you to install graphics cards, sound cards, TV tuners, wireless cards, and other cards labeled as “expansion” cards.

PCI-E comes in four different types of slots. x16, x8, x4, and x1 and these numbers designate the speed and size of the slot. While ATX boards are standardized, the types of PCI-E slots they offer can vary depending on the cost of the board. It’s always important to check what a motherboard offers before you buy, however, it should be noted that modern boards almost always have at least one PCE-I x16 slot.

PCI-E x16 slots are the most important slot for graphics cards because almost all modern cards require a x16 slot because their larger size means they can’t fit in a smaller slot. A x16 slot is also required for a high end video card to operate at its fastest speed. You need at least one PCI-E x16 slot to use a high end graphics card, and if you intend to bridge two cards together you will need two of these slots.

As a small aside on PCI-E x16 slots, when looking at modern cards from both Nvidia and AMD, you will find that they claim to require different generation slots. Generation 3 is the newest, while AMD will often claim to require generation 2. You don’t need to worry about this. Since most modern motherboards ship with generation 3, any card requiring generation 2 will work perfectly fine in these newer slots. This is a needlessly odd complication by video card manufacturers that really needs to be correct in my opinion.

Other expansion style cards will say what type of PCI-E slot they require. If you intend to buy a TV tuner or wireless card for example, ensure that your motherboard has the right slot size for them. Unless you’re absolutely overloading your board with expansion slots though, you should not have anything to worry about in this regard.

 

Understanding the Backbone of Your PC (Conclusion)

If you were to claim that the CPU is the brain of your computer, then it’s undeniable that the motherboard is the backbone. Without the motherboard, none of your computer’s components could function properly and they would all lay uselessly in a pile at the bottom of your computer case. It truly earns its title of being a motherboard, because without it, none of the potential of your PC could be brought out and no communication would happen between your components.

Now that you know more about motherboards, I hope you feel more confident in discussing them with others, or using the knowledge you learned to make a more informed purchase for your new system build!

If you have any comments or questions, be sure to leave them below and I will do my best to respond to you directly!

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