Motherboards | CompTIA A+ 220-1001 | 3.5

In this video you will learn about various motherboard components, CPUs, and add-on cards.

A motherboard (also known as a mainboard, system board and logic board) is the main printed circuit board in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals.

Motherboard Form Factors

Form factor is a hardware design aspect that defines and prescribes the size, shape, and other physical specifications of components, particularly in electronics. It may also define an entire system, as in a computer form factor. Computer chassis are designed to accommodate specific form factors, and knowing these common standard form factors is essential for an A+ technician:

  • ATX (Advanced Technology eXtended)
  • mATX (microATX)
  • ITX (Information Technology eXtended)
  • mITX (Mini-ITX)

ATX (Advanced Technology eXtended)

ATX is a motherboard and power supply configuration specification developed by Intel in 1995 to improve on previous de facto standards like the AT design. It was the first major change in desktop computer enclosure, motherboard and power supply design in many years, improving standardization and interchangeability of parts. The specification defines the dimensions; the mounting points, the I/O panel; and the power and connector interfaces among a computer case, a motherboard, and a power supply. An ATX motherboard has the following characteristics:

  • A rear port cluster for I/O ports
  • Expansion slots that run parallel to the short side of the motherboard
  • Left-side case opening (as viewed from the front of a tower PC)
ATX Motherboard

There are three members of the ATX family, although in practice, the mITX design is not widely used.

ATX Motherboard Family Comparison

ITX (Information Technology eXtendend)

ITX is a small motherboard form factor from VIA Technologies that was first introduced in November 2001 with the Mini-ITX (mITX) for use with its low-power CPUs that are soldered to the motherboard. Mini-ITX (mITX) measures 6.7×6.7 inches and has been adopted by many vendors for use with AMD and Intel processors. mITX motherboards can fit into cases made for ATX-family motherboards & use similar port clusters, although they are primarily used for small form factor PCs for 3D video & gaming as well for use in home theater applications

ATX, mATX, & mITX Form Factors

Motherboard Connector Types

Motherboards use expansion slots to provide support for additional input/output (I/O) devices and high-speed video/graphics cards with the most common expansion slots being PCI Express (PCIe).

PCI Slots (Peripheral Component Interconnect)

A PCI slot is a built-slot on a device that allows for the attachment of various hardware components such as network cards, video, I/O, storage host adapters for SATA drives, modems, sound cards, disk controllers and other peripherals. PCI slots found in desktop computers are 32-bit and run at 33MHz, whereas in 64-bit versions, PCI slots run at 66MHz.

PCI Slots

PCIe (PCI Express) Slots

PCIe is a high-speed serial computer expansion bus standard designed to replace the older PCI bus standards. It is the common motherboard interface for PC’s graphics cards, hard drives, SSDs, WiFi and Ethernet hardware connections. PCIe has numerous improvements over the older standards, including higher maximum throughput, lower I/O pin count and smaller physical footprint, better performance scaling, a more detailed error detection and reporting mechanism, and native hot-swap functionality. More recent versions of the PCIe standard provide hardware support for I/O virtualization. PCIe slots are available in four types: x1, x4, x8, & x16. (Each x refers to an I/O lane.) The most common versions are the x1, x4, and x16.

PCIe Slots

Riser Cards

A riser card is a printed circuit board that picks up a multitude of signal lines (often bused) via a single connector (usually an edge connector) on a motherboard and distributes them via dedicated connectors on the card. Riser cards are often used to allow adding expansion cards or multiple ports available to a system enclosed in a low-profile case where the height of the case does not allow for a perpendicular placement of the full-height expansion card.

Typical Riser Card
Riser Card Connections

Socket Types

In computer hardware, a CPU socket (CPU slot) contains one or more mechanical components providing mechanical and electrical connections between a microprocessor and a printed circuit board. This allows for placing and replacing the CPU without soldering. Common sockets have retention clips that apply a constant force, which must be overcome when a device is inserted. For chips with many pins, zero insertion force (ZIF) sockets are preferred. Common sockets include Pin Grid Array (PGA) or Land Grid Array (LGA). These designs apply a compression force once either a handle (PGA type) or a surface plate (LGA type) is put into place. This provides superior mechanical retention while avoiding the risk of bending pins when inserting the chip into the socket.

Zero insertion force (ZIF) is a type of integrated circuit (IC) or electrical connector that requires very little force for insertion. With a ZIF socket, before the IC is inserted, a lever or slider on the side of the socket is moved, pushing all the sprung contacts apart so that the IC can be inserted with very little force, generally the weight of the IC itself is sufficient and no external downward force is required. The lever is then moved back, allowing the contacts to close and grip the pins of the IC. ZIF sockets are much more expensive than standard IC sockets and also tend to take up a larger board due to the space taken up by the lever mechanism. Typically, they are only used when there is a good reason to do so.

Typical ZIF Socket

The LGA is a packaging technology with a rectangular grid of contacts (“lands”) on the underside of a package. The LGA design uses spring-loaded lands in the processor socket that connect to bumps on the backside of the processor. The number of lands in the processor socket is used for the numeric part of the socket name.  For example, LGA 775 has 775 lands in the processor socket. Not all rows and columns of the grid need to be used. The contacts can either be made by using an LGA socket, or by using solder paste.

Typical LGA Socket

A pin grid array (PGA) is a type of integrated circuit packaging. In a PGA, the package is square or rectangular, and the pins are arranged in a regular array on the underside of the package. The pins are commonly spaced 2.54mm apart, and may or may not cover the entire underside of the package. PGAs are often mounted on printed circuit boards using the “through hole” method or inserted into a socket. PGAs allow for more pins per integrated circuit than older packages.

Typical PGA socket

SATA (Serial ATA) & IDE (Integrated Drive Electronics)

Serial ATA is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives adjacent to the CPU. SATA connectors replaced IDE connectors, which were ribbon-like cables for CD-ROMs/DVDS or a hard drive that were slower and more cumbersome and that needed to be assigned priority. SATA also succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices. The most important improvement was speed, with first-generation SATA cables transferring data up to 1.5Gbps. As SSDs came to market, SATA specification improved to 3Gbps to match the faster data capabilities of the solid-state drives.  The latest SATA version transfers data at 6Gbps.

SATA Connector
SATA Cable
IDE Connector
IDE Cable

Front & Top Panel Connectors

Typical motherboards feature one or more audio connectors designed for different purposes:

  • Front/top-panel audio:  Microphone and headphones; found on almost all motherboards.
  • Music CD playback from optical drives:  Rarely needed feature because media player programs can play music through the SATA interface.
  • SPDIF header:  Designed to support an optional SPDIF bracket for digital audio playback.
Front & Top Panel Connectors

ATX and ITX-family motherboards include front/top-panel connectors for the power button, power light, drive activity lights, reset button, USB, and audio case speaker (if present).  These connectors are grouped together on or near the front edge of the motherboard.

ATX & ITX Front/Top-Panel Connectors

Internal USB Connector

The USB connector on the outside of the case or laptop need to connect to the motherboard so that external devices can access the motherboard.

Internal USB Connector
9-Pin USB Connector

BIOS/UEFI Settings

BIOS (Basic Input/Output System) is a ROM chip found on motherboards that allows you to access and set up your computer system at the most basic level. The Unified Extensible Firmware Interface (UEFI) is a specification interface between an operating system and platform software. UEFI is the first code run by a computer when it is booted by preparing the machine by testing it during bootup and paves the way for the operating system to start. It tests and initializes components such as the processor, RAM, video card, hard drives, optical drives, and USB drives. If any errors occur, the BIOS/UEFI reports them as part of the testing stage, known as the power-on self test (POST). To access the BIOS, press the key or key combination displayed on the screen when the system starts booting to access the BIOS program menu. UEFI, which is a GUI or text-based menu, replaced the legacy BIOS firmware interface in most PCs, with most UEFI firmware implementations providing support for legacy BIOS services. UEFI can support remote diagnostics and repair of computers, even with no operating system installed. All Mac computers use UEFI firmware.

Typical BIOS

Advantages of UEFI:

  • Support for hard drives of 2TB and higher capacity.  These drives require the use of the GUID Partition Table (GPT) to access full capacity.
  • Faster system startup (booting) and other optimizations.
  • Larger-size ROM chips used by UEFI make room for additional features, better diagnostics, the ability to open a shell environment for easy flash updates, and the ability to save multiple BIOS configurations for reuse.
Typical UEFI

Boot Options:  Settings and Boot Sequence

Most computers include settings that control how the system boots and the sequence in which drives are checked for bootable operating system files.  Depending on the system, these settings might be part of a larger menu, such as an Advanced Settings menu, a BIOS Features menu, or a separate Boot menu.

Firmware Updates

General steps to locate a flash BIOS update and install it:

  1. Go to the vendor’s website and look for “downloads” or “tech support” links.  The BIOS updates are listed by system model and by version; avoid beta (prerelease) versions.
  2. Locate the correct BIOS update for your system or motherboard.
  3. Determine the installation media needed to install the BIOS image (Windows-based installer, bootable CD, or USB flash drive).
  4. Download all files needed to install the BIOS image.
  5. Create bootable media and then follow the vendor’s instructions to place the loader and BIOS image files on the media.
  6. Installation
    1. Bootable media: Make sure the drive is the first item in the BIOS boot sequence.  Insert or connect your media and restart the system.  If prompted, press a key to start the upgrade process.  After the process starts, it takes approximately three minutes to rewire the contents of the BIOS chip with the updated information.
    2. Windows: Close all Windows programs before starting the update process.  Navigate to the folder containing the BIOS update and double-click it to start the update process.  Follow the prompts onscreen to complete the process (takes approximately 3 minutes).
  7. Remove the media and restart the system to use your new BIOS features.  Reconfigure the BIOS settings if necessary.

Caution:  While performing a flash upgrade, make sure you don’t turn off the power to your PC.  Wait for a message indicating that the BIOS update has been completed before touching the computer.  If the power goes out during the flash update, the BIOS chip could be rendered useless.

Security Features

Security features of various types are scattered around the typical system BIOS/UEFI dialogs.  Features and their locations vary by system and might include:

  • BIOS password:  BIOS Settings Password or Security dialogs. Enable BIOS password to feature permit access to BIOS setup dialogs.
  • Power-on password:  Configured through the Security dialog. Prevents anyone without a password from starting system.
  • Chassis intrusion:  Various locations
  • Boot sector protection:  Advanced BIOS Features dialog

Note: BIOS password & Power-on password can be overcome by opening the system & clearing the CMOS memory.

These features support drive encryption:

  • TPM (trusted platform module):  Security dialog. Windows editions that support BitLocker FDE (full-disk encryption) feature TPM to protect the contents of any specified drive.
  • LoJack for laptops:  After-market product embedded in firmware or installed by the end-user; not managed with BIOS dialogs. Used for locating lost/stolen laptops.
  • Secure Boot:  Boot or other dialogs. Blocks installation of other operating systems & requires the user to access UEFI setup by restarting the computer in a special troubleshooting mode within Windows 8 or later.

Interface Configurations

Interface configurations consist of:

  • SATA configurations options: To enable/disable SATA & eSATA ports & to configure SATA host adapters to run in compatible, native, or RAID modes.
  • USB host adapters & charging support: Used to enable USB 2.0 & 3.0 in your system BIOS so that all your system’s USB ports will run at proper speeds.
  • Audio & Ethernet ports: Used to configure audio & ethernet ports and other integrated ports

CMOS Battery

The CMOS (complementary metal-oxide semiconductor) battery maintains the time, date, hard disk and other configuration settings in the CMOS memory. CMOS batteries are small and are attached directly to the motherboard. The CMOS battery provides power to maintain the contents of the CMOS chip. Battery life is several years, but a low CMOS battery can cause problems with drivers and sometimes booting. System date & time errors can be an indication that it is time to check or change out the battery.

CMOS Battery

To clear CMOS on most systems, place a jumper block over two jumper pins. Some systems feature a port-cluster-mounted push button to clear the CMOS.

CPU Features

CPU Cores:  Single Core & Multicore

A single core is a chip with one CPU (processing unit) that receives instructions from software to perform calculations for output.

Multicore processors are computer processor integrated circuits with 2 or more separate processing units which read and execute program instructions, as if the computer had several processors. The benefits of a multicore processor versus having multiple physical processors is a reduction on price and they work with any operating system that supports traditional single-core processors.

Single-Core vs. Multicore Processors


CPU virtualization emphasizes performance and runs directly on the processor whenever possible. The underlying physical resources are used whenever possible and the virtualization layer runs instructions only as needed to make virtual machines operate as if they were running directly on a physical machine. Most current processors feature virtualization support, also known as hardware-assisted virtualization. Hardware-assisted virtualization enables virtualized operating systems and applications to run faster and use fewer system resources.


Hyperthreading is Intel’s proprietary simultaneous multithreading implementation used to improve parallelization of computations (doing multiple tasks at once) performed on x86 microprocessors. When hyperthreading is enabled in the system BIOS and the processor is running a multithreaded application, the processor is emulating two physical processors.

CPU Speeds

A bus is a circuit that connects one part of the motherboard to different components such as the CPU, memory, chipsets, expansion slots, storage interfaces, and I/O ports. The more data a bus can handle at one time, the faster it allows information to travel. The speed of the bus, measured in MHz, refers to how much data can move across the bus simultaneously.


In computing, the purpose of overclocking is to increase the operating speed of a given component. On modern systems, the target of overclocking is increasing the performance of a major chip or subsystem, such as the main processor or graphics controller, but other components, such as system memory (RAM) or system buses are commonly involved. The trade-offs are an increase power consumption (heat), fan noise (cooling), and shortened lifespan for the targeted components. Most components are designed with a margin of safety to deal with operating conditions outside of a manufacturer’s control. Overclocking techniques in general aim to trade this safety margin by setting the device to run in the higher end of the margin, with understanding that temperature and voltage must be more strictly monitored and controlled by the user.

Integrated Graphics Processing Unit (GPU)

An integrated graphics processing (IGP) unit is a graphics chip that is integrated into a computer’s motherboard. The IGP serves the same purpose as a video card, which is to process the graphics displayed on the computer. IGP take the graphics portion of the processing load off the main CPU. Due to IGPs being soldered onto the motherboard, their size is limited and they cannot use a dedicated fan to cool them, like some video cards do. This is the main reason as to why IGPs typically do not have the same performance as video cards that are attached to the computer’s PCI or AGP ports. IGPs due to their small size are good solutions for laptop computers and entry-level desktop PCs.

Processor Compatibility

AMD & Intel are the two main companies for producing CPUs. AMD processors use the Pin Grid Array (PGA) form factor where the contact pins that insert into the socket are mounted to the CPU itself. Intel processors use the Lang Grid Array (LGA) form factor where the pins that connect to the CPU to the motherboard are mounted on the motherboard’s socket. Due to how the CPUs physically attach and how they work internally means that the two brands are not compatible with one another. Independent manufacturers of motherboards, such as ASUS and ASRock, make several different boards that support CPUs from both companies.

Cooling Mechanisms

Computer cooling is required to remove the waste heat produced by computer components, to keep components within permissible operating temperature limits. Components that are susceptible to temporary malfunction or permanent failure if overheated include integrated circuits such as CPUs, chipsets, graphics cards, and hard disk drives. The basic requirements for proper CPU cooling include the use of an appropriate active heat sink (which includes a fan) and the application of an appropriate thermal material (grease, paste, or a pre-applied thermal or phase-change compound).  Advanced systems sometimes use liquid cooling instead.

Fan & Heat Sink

A heat sink is a finned metal device that radiates heat away from the processor.

CPU Fan & Heat Sink

Thermal Paste

Before installing a heat sink bundled with a processor, remove the protective cover over the pre-applied thermal material (also known as phase-change material) on the heat sink.  When the heat sink is installed on the processor, this material helps ensure good contact between the CPU and the heat sink to maximize heat transfer away from the CPU.

CPU Thermal Paste

Liquid-Based Cooling

Liquid cooling systems involve attaching a liquid cooling unit instead of an active heat sink to the processor and other supported components.  A pump moves the liquid (which might be water or a special solution, depending on the cooling system) through the computer to a heat exchanger, which uses a fan to cool the warm liquid before it is sent back to the processor. Liquid cooling systems are designed primarily for high-performance systems, especially overclocked systems.

CPU Liquid Cooling System

Expansion Cards

An expansion card is an electronic card/board that is used to add extra functionality to a computer. It is inserted into an expansion slot on the motherboard of a computer. Expansion cards contain edge connectors that are used to create an electronic link between the motherboard and card, thus enabling these two to communicate.

Video Cards

A video card (graphic card) is an expansion card which generates a feed of output images to a display device (such as a computer monitor). Most video cards are not limited to simple display output. Their integrated graphics processor can perform additional processing, removing this task from the central processor of the computer. Video cards can come as onboard or as add-on cards.

Video Card

Sound Cards

A sound card is an expansion card for an integrated circuit for producing sound on a computer that can be heard through speakers or headphones. Although the computer doesn’t need a sound card, it’s included on every machine as either in an expansion slot or built into the motherboard (onboard).

Typical Sound Card

Network Interface Card (NIC)

A NIC is a computer hardware component that connects a computer to a computer network using an Ethernet cable with an RJ-45 connector.


USB Expansion Cards

USB expansion cards provide more USB ports to support additional connections.

USB Expansion Card

eSATA Card

eSATA expansion cards provide more eSATA ports to support additional connections to devices utilizing eSATA connectors. eSATA is not as common as SATA, but eSATA has been widely used by high-performance Windows and Linux-based desktop computers for external hard drives.

SATA & eSATA Drive Interface Overview