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What Does a PCI Express Slot Look Like? – Learn Here

Peripheral components require slots on the computer for connections. These are known as PCIe Slots and they are different from all other slots. If you are wondering what does a PCI Express Slot look like, you have come to the right place.

PCI Express slots will look different depending on their sizes, X1, X4, X8, and X16. It’s a rectangular slot with terminals inside. There’s a ridge that separates it into two parts. The first one is constant across all slots and the second part varies depending on lane count. 

These slots will often be found on the part of the motherboard that’s closest to the computer’s case IO shield. That’s because many expansion cards that go into PCIe slots expose some ports outside the computer.

In the following text we will look detail into what does a PCIe slot looks like.

What Does a PCI Express Slot Look Like?

PCIe Sizes
PCIe Slots come commonly in x1, x4, x8 and x16 sizes. X8 is rarely seen as it is merely replaced by X16 size working in X8 mode.

You may have heard that these slots are responsible for attaching extra expansion cards to your computer.

They do so by having terminals that are responsible for data transmission, also known as lanes; as well as terminals that supply power to the devices.

The first part of the PCIe connection is fixed. All the slots have this part, it’s constant regardless of the PCI Express slot.

This first part ends at the ridge that’s also known as the hardware key. Its use is to ensure that only the right component is installed in the correct PCIe slot. Any other non-PCIe device won’t fit inside the slot thanks to this.

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The Fixed Part

The first part consists of eleven terminals on either side of the PCIe slot, making a total of 22 terminals.

These are responsible for numerous things including the 12-volt power supply that powers the device connected to it.

It measures about 11.65mm in length. The slot itself comes in at about 11.25mm in height from the mounting surface on the board to the top.

The Variable Part

pcie Sizes
Image Source: ccboot.com

The second part that comes after the mechanical key varies depending on the physical measurement of the slot.

The X1 slot is the smallest while the largest slot on mainstream motherboards is the X16. There is, however, an X32 slot but it is very rare.

The biggest factor that determines the size of the slot is the number of lanes it accommodates. That is, the more the lanes, the larger the slot will be.

But this is not always the case as you can find an X16 slot with only four lanes.

To better understand what does a PCI Express Slot look like, let’s go through the available slots.

X1 Slot

This is the smallest slot on the motherboard in terms of physical lanes. It has only one data lane that consists of a transmitting and a receiving wire.

That said, the slot measures about 25 mm in length. On it, there are a total of 18 working pins, including the first 11.

X4 Slot

This slot has four times the lanes in an X1 slot. However, it measures just about 39mm in length. The slot has a total of 32 pins inside.

This slot will appear slightly longer on the motherboard than the X1 slot. It is however still shorter than the next one.

X8 Slot

The X8 slot is ideal for high bandwidth devices. That said, it has twice as many lanes as the X4 slot and is capable of taking even a graphics card if open-ended.

It measures 56mm in length, meaning despite its high lane count, it doesn’t take up a lot of space on the motherboard.

You also get about 49 pins on this slot, and this includes the first 11 pins.

X16 Slot

This is the largest slot on the motherboard and is used by devices that have the highest bandwidth requirements.

It offers the highest mainstream performance for any PCIe generation and it comes up at about 89mm in length.

With this, it houses 82 pins which include a total of 16 data transmission lanes.

Things to Consider

How to Unlock PCIe Slot Clip
Unlocking Mechanism on Certain PCIe slots. Source: Dell.com

Some PCIe slots come with ridges. These can be found on one side of the connectors’ housing. They serve the purpose of card retention; that is, firmly holding the card in place to prevent wiggling or getting dislodged.

You also get a retention clip with some PCIe slots. This is even more common with the PCIe X16 slot which is popular with a graphics card.

Because the said cards are large, they need to be firmly held onto the slot and this is where the clip comes in. You can use it to identify the PCIe slot. Furthermore, you usually get the clip on just one end of the PCIe slot.

What are Reinforced PCIe Slots?

What Does a PCI Express Slot Look Like
The first PCIe x16 slot (colored silver) is reinforced.

Its construction also tells us what does a PCI Express slot look like. Many PCIe slots are made entirely out of plastic. This is ideal because the material is capable of providing a very rigid support for the devices. This is also because plastic is an insulator.

This ensures that contacts do not close circuits and end up shorting out the PCIe slot which can ruin the motherboard or installed PCIe cards.

Some PCIe slots come with reinforcement though. This helps keep the cards in place when you are moving or in case of falls. This can make it difficult to determine what does a PCIe Express slot look like, but the underlying bits will still make them easy to identify.

Usually, the first X16 slot of a motherboard that would house a heavy graphics card is reinforced so that it does not break apart.

If a motherboard support two graphics card, then you will find two reinforced PCIe x16 slots.

two pcie x16 reinforced PCIe slot
Motherboard with two PCIe x16 reinforced slots and one normal. Image Source: Guru3d.com

Also Read: Best Motherboards for SLI

How Durable are PCIe Slots?

PCIe slots are durable enough to handle graphics that can weight as much as 1 KG or 2.2 pounds.


Hopefully, this makes it easier to tell what does a PCI Express slot look like. There are two parts here. The first part is usually fixed for all PCIe slots. It is the second part that varies according to the lane count of the slot.

They are mostly made out of plastic and have some pins on either side of the slot. A key notch ensures that only the correct devices are installed in a particular slot.

Furthermore, you get some retention clips on some as well as metal reinforcement to provide a firm fit for the installed cards.

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