3.11.1 Expansion Buses & Slots

Learn how expansion cards enable aging systems to keep up with the latest features and upgrades.

In the olden days of computing, when a new feature released and you wanted your PC to have it, there was no other way to get that feature except scrapping your old PC and buying an entirely new one with that feature. Modern motherboards now have expansion slots that you can plug expansion cards into to gain new features and capabilities that the base system didn't have.

However, the cards and slots are designed to use particular communication standard and physical characteristics specification, making most expansion bus standards not compatible with one another. When installing an expansion card, you'll need to identify the bus type used by both the expansion card and your motherboard's expansion slots. Two key characteristics include the card and slots length and how it's keyed.

Peripheral Component Interconnect (PCI)

PCI expansion cards have a connector tab that is keyed. The notch is placed towards the back of the card, corresponding with a motherboard's PCI expansion slot. The keyed tab prevents installed a card in the wrong expansion slot interface or even backwards.

PCI Extended (PCI-X)

Designed to enhance the original PCI standard, PCI-X expansion cards have double the length of the standard PCI cards, granting them a doubled data transfer speed compared to the original.

PCI and PCI-X cards are older interfaces, with the next generation of PCI essentially replacing them. You'll now only find PCI-X expansion cards installed in server systems.

PCI Express (PCIe)

The PCI Express interface is much faster than the standard PCI, and it allows for more functionality and features. It has two connection formats:

PCIe x1

It looks like a miniature PCIe card, and it's typically used for network interface cards or dedicated sound cards.

PCIe x16

More similar in length to the standard PCI card, the PCIe x16 has it's notch near the front of the card and slot, opposite of the standard PCI. As it's name suggests, it 16 times faster then the PCIe x1 interface. This speed is usually used by dedicated video cards.

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