What Are the Slots on a Motherboard?

A motherboard is the central printed circuit board (PCB) in 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.

Slotting into the motherboard are expansion cards which add functionality to the computer, such as graphics cards or network cards. The slots on a motherboard therefore allow you to expand the capabilities of your computer system.

The most common type of expansion slot today is called a PCI Express (PCIe) slot. PCIe slots come in different sizes which are measured in lanes.

A PCIe x1 slot has one lane and can transfer data at up to 250 MB/s, while a PCIe x16 slot has 16 lanes and can transfer data at up to 4 GB/s. There are also larger slots for specialised applications such as graphics cards or solid state drives (SSDs).

The second most common type of expansion slot is the older PCI slot. These are much larger than PCIe slots and usually have white plastic tabs at either end.

They support data transfer speeds of up to 133 MB/s.

There are also a few less common types of expansion slots, such as AGP, ISA and AMR/CNR. AGP was once used for graphics cards but has been replaced by PCIe.

ISA slots were used for a variety of expansion cards in the past but have now been mostly superseded by PCI and PCIe slots. AMR/CNR slots were once used for modems but are no longer needed as most computers now have integrated modem functionality.

The slots on a motherboard therefore provide you with options for expanding the capabilities of your computer system. If you want to add a new graphics card or network card, for example, you will need an available PCIe slot.