Hardware · Topic 7 of 13
Motherboards and Expansion Cards
Identify motherboard form factors, sockets, memory and PCIe slots, front panel and fan headers, and install add-on cards such as graphics cards.
- 5 min
- ATX is the full size standard, micro ATX is smaller, mini ITX is the smallest of the three.
- A smaller board fits a larger case, but not the other way around.
- The socket must match the CPU, and the RAM slots must match the memory generation.
What it is
The motherboard is the main circuit board. Every other part plugs into it, so its size, sockets and slots decide which parts a computer can use.
Add-on cards plug into expansion slots to add functions such as better graphics, extra network ports or special storage controllers.
How it works
Form factors
The form factor sets the size, mounting holes and layout. The case must support the board's form factor.
| Form factor | Notes |
|---|---|
| Advanced Technology eXtended (ATX) | Standard full size board with the most slots |
| Micro ATX | Smaller than ATX, with fewer expansion slots; fits ATX cases |
| Mini Information Technology eXtended (ITX) | Very small board with usually one expansion slot |
A smaller board fits a larger case, but a larger board does not fit a smaller case.
Main parts of the board
- Central processing unit (CPU) socket: holds the processor and must match the processor type.
- Chipset: the group of chips that links the CPU with memory, storage and devices, and decides which features the board offers.
- Memory slots: hold random access memory (RAM) modules, and the generation must match.
- Expansion slots: Peripheral Component Interconnect Express (PCIe) slots for add-on cards.
- Storage connectors: Serial Advanced Technology Attachment (SATA) ports and M.2 slots.
- Power connectors: the main 24 pin connector and a 4 or 8 pin CPU power connector.
- Complementary metal oxide semiconductor (CMOS) battery: a small coin cell that keeps the clock and settings.
- Headers: small groups of pins for the case and extra ports.
PCIe slots
PCIe slots are named by lanes: x1, x4, x8 and x16. More lanes means more bandwidth.
A small card fits in a larger slot, so an x1 card works in an x16 slot. Graphics cards need an x16 slot.
Older Peripheral Component Interconnect (PCI) slots are found on old boards only and are not the same as PCIe. PCIe generations (such as 3, 4 and 5) raise the speed per lane while keeping the same physical slot shape.
Headers
| Header | Purpose |
|---|---|
| Front panel | Power switch, reset button and drive and power lights; the pins are labelled in the manual |
| Universal Serial Bus (USB) header | Front USB ports on the case |
| Audio header | Front headphone and microphone jacks |
| Fan headers | Power and control for fans, in 3 pin or 4 pin versions; 4 pin supports pulse width modulation (PWM) speed control |
| RGB header | Powers red, green and blue (RGB) lighting strips |
Front panel pins are small and easy to place wrongly. Use the diagram printed on the board or in the manual.
Add-on cards
| Card | Function |
|---|---|
| Video (graphics) card | Draws the picture and offloads work from the CPU; may need extra power cables |
| Sound card | Better audio input and output |
| Network interface card (NIC) | Adds wired or wireless network ports |
| Storage controller | Adds extra SATA ports or drive array features |
| Capture card | Records video from external sources |
| USB or Thunderbolt card | Adds extra ports |
| Riser card | Turns a slot at an angle, used in thin cases and servers |
Installing a card
- Power off, unplug and use electrostatic discharge (ESD) protection.
- Remove the slot cover from the back of the case.
- Line up the card with the slot and press it in firmly until it seats.
- Fasten it with a screw at the bracket.
- Connect any extra power cable (a graphics card often needs one).
- Start the computer and install the driver from the maker.
An x16 graphics card in an x16 slot with no extra power connected is a common reason for a blank screen or boot beeps. Check the cable first.
Matching parts
A new board must match the CPU socket, the RAM type, the case size and the power supply connectors. When swapping a board, reconnect the case front panel, fans and drives, and install the rear input and output (I/O) shield.
What to remember for the exam
- ATX is the full size standard, micro ATX is smaller, mini ITX is the smallest of the three.
- A smaller board fits a larger case, but not the other way around.
- The socket must match the CPU, and the RAM slots must match the memory generation.
- PCIe slots are x1, x4, x8 and x16; smaller cards fit in larger slots.
- Graphics cards use an x16 slot and often need an extra power cable.
- The CMOS battery keeps time and settings.
- 4 pin fan headers allow PWM speed control.
- Add-on cards need drivers.
Common mistakes
Forgetting card power. High end graphics cards need extra power from the supply.
Mixing front panel pins. The power switch and reset header pins are easy to confuse; follow the manual.
Ordering the wrong board size. Check the case support before buying.
Using the wrong slot for a card. A card should go into a slot with at least as many lanes as it needs.
Skipping drivers. A card may work poorly or not at all without the maker's driver.
Check yourself
Which form factor is the smallest of ATX, micro ATX and mini ITX?
Mini ITX.
Can an x1 PCIe card be used in an x16 slot?
Yes, a smaller card works in a larger slot.
What does the CMOS battery do?
It keeps the real time clock and firmware settings when the computer is off.
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