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PCIe Slots and Their Uses

Pcie Slots
Quick Answer

Peripheral Component Interconnect Express slots – often simply called PCI Express – allow for connecting components directly to your motherboard. The most important part that uses PCI Express is the graphics card, but lots of other components use this as an interface as well.

In the rest of the article, we will learn what a PCI Express slot is by looking at what it does, the different sizes it comes in, and a bit about its history. We’re also going to look at some of the most common components that use PCI Express as an interface.

What is a PCI Express Slot?

PCI Express is an expansion bus standard, which in simplest terms, means that it is an interface used to connect certain computer components to your PC’s motherboard. PCI Express is part of a move toward making interfaces more universal, having replaced multiple of its predecessors.

Sizes of PCI Express Slots

PCI Express slots are not all identical. They differ based on the number of lanes they have. The slots can have either one, four, eight, or sixteen lanes, with the slot increasing in width to accommodate the number of lanes. These sizes are represented by a number following an “x” – for example, an eight-lane slot can be written as “PCIe x8.”

PCI Express cards don’t have to fit into slots of their exact size. A card can also be inserted into a slot that has more lanes than the card itself, and it will run. Due to the way the interface works, PCI Express cards cannot be inserted into slots with fewer lanes than the card.

History of PCI Express

PCI Express was first created in 2003. Over the next few years, the interface slowly superseded its direct predecessor, PCI, and PCI-X, which is often confused due to the similarity in the names. PCI Express also superseded the Accelerated Graphics Port (AGP) interface, which had been the standard for graphics cards until then.

Do Graphics Cards Use PCIe?

Graphics cards today all use the PCI Express interface. This is an essential component for almost all computer users. Many motherboards come with integrated graphics chipsets, but these are only suitable for the most rudimentary computer usage. Anything beyond that and certainly most gaming will require a dedicated graphics card.

Graphics cards used to use the AGP interface, but this standard has not been in practice for long. Graphics cards today all require a PCI Express port, but the good news is that all motherboards will come with this interface, though how many slots you get depends on the motherboard model.

Graphics cards will tend to use the 16 lane PCI Express slot, so if you have any other smaller peripherals, it is better to use the smaller slots rather than fit them into what is usually the only 16 lane slot on a motherboard, even though they will also work there. This allows the 16 lane slot or slots to be used for graphics cards.

If your motherboard has two 16 lane PCI Express slots and they are appropriately spaced out, you can use this interface to run two graphics cards simultaneously. You will need to connect them with a bridge, and there are restrictions to whether they will work together, but you can find more details about this on AMD’s Crossfire page and Nvidia’s SLI page.

Do Network Cards Use PCIe?

Network functionality tends to be built into motherboards, so this one might not seem necessary, but there are many scenarios where you may want to add a network card to your computer, which will connect via PCI Express.

An ethernet card might seem extraneous, but the right ones will offer far greater speed than integrated Ethernet solutions. This is especially useful if your computer is used in a setting where massive amounts of data need to be transferred over local area networks often.

The wireless network adapter is another type of network card that can connect to a motherboard via its PCI Express slot. Although it is more common to get these as dongles that connect to a USB port now, you can still get them as expansion cards which might have greater capabilities.

Do Sound Cards Use PCIe?

Dedicated sound cards are not as common as they once were. Every modern motherboard will have sound processing hardware built into it and the audio ports needed to connect peripherals to it. Even modern graphics cards will have sound components to transfer audio through HDMI ports.

If you work in audio production, do it as a hobby, or even just want the best sound experience you can get, you can still get a dedicated sound card to enhance your audio quality. These sound cards will connect to your motherboard via the PCI Express interface.

Can I Use PCIe to Add Another M.2 Slot?

Motherboards will not have many M.2 slots, which is a shame considering their usefulness. However, you can utilize your motherboard’s PCI Express slots to attach expansion cards that themselves offer the M.2 interface. These expansion cards will tend to use four-lane slots.

Using PCI Express slots to add more M.2 interfaces is a very good trick because this interface offers greater speed for solid-state drives compared to when they are connected via SATA cables. An SSD connected through an M.2 expansion card in a PCI Express slot can operate 35 times faster than a hard disk drive even when the HDD is under ideal conditions.


We’ve learned precisely what PCIe slots are and their uses by starting with the interface’s history and how it became a universal standard for expansion cards. We’ve also looked at multiple components that make use of the PCI Express interface to connect to your motherboard, including graphics cards, network cards, sound cards, and expansion cards that add M.2 slots to your computer.

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