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How Many PCIe Slots Do I Need?

Pcie Slots
Quick Answer

How many PCI Express slots you need for your computer will depend on what you are using it for. At least one PCIe x16 slot is necessary to attach a dedicated graphics card, a second one is needed to run two graphics cards, and other slots will be required to connect different components that use the interface.

In the rest of the article, we will look at what PCI Express slots are used for, the different types of PCI Express slots, and how many of these slots you might need in a gaming computer for solid-state drives and other components.

What is PCIe Used For?

Peripheral Component Interconnect Express – or PCI Express for short – slots connect additional components to your motherboard. This format has replaced multiple of its predecessors, which means that you can use it for many different expansion cards and even to connect solid-state drives.

Because of their almost universal nature, you will need to pay close attention to how many PCI Express slots any motherboard you are planning to buy has. Think about what components you will want to connect at the time and in the future, and make sure the motherboard you’re buying has enough slots for everything.

Are There Different Types of PCIe Slots?

Not all PCI Express slots are the same. They will have different numbers of lanes. When looking at the specifications of a motherboard or an expansion card, the number of lanes will be written as a number followed by an “x.” A 16-lane PCI Express slot or expansion card, for example, can be written as “PCIe x16.”

A PCIe expansion card doesn’t need to be fit into a slot with the same number of lanes as itself. Components can also be fitted into slots with a higher number of lanes than the card requires. Because of their physical structures, you cannot insert an expansion card into a PCI Express slot with fewer lanes than the card requires.

This wider compatibility is very convenient, but you should still be careful with which cards you use in which slots. Motherboards will typically come with fewer PCIe x16 slots than those of smaller sizes. Because these slots are essential for graphics cards, you do not want to waste them on components that can fit into smaller slots.

How Many PCI Express Slots Should a Gaming Computer Have?

If you are building a computer for gaming, you will need at least one PCIe x16 slot. Even though many motherboards will have integrated graphics chipsets, these are rarely good enough to play more than a small selection of games, so a graphics card is necessary.

Graphics cards will tend to use the 16 lane PCI Express slot. It is standard for motherboards to come with at least one suitable slot for this, but if they have few others, you might have to choose whether to use it for your graphics card or a less essential component.

For this reason, you should always make sure to factor in all components you plan to connect to your gaming computer rather than only your graphics card.

You might also choose to have more than one graphics card. If you want to do this, the motherboard you are buying will need to have two 16 lane PCI Express slots that are correctly spaced out to fit two graphics cards and the bridge that connects them.

Be aware that even if you have two or more PCIe x16 slots, connecting multiple graphics cards will not work. There are conditions to running two graphics cards together, and you can find the details out on Nvidia’s SLI page for that manufacturer’s cards and AMD’s Crossfire page for theirs.

How Many PCI Express Slots Do I Need for SSDs?

Motherboard manufacturers limit the number of M.2 slots that come standard with their products, but this can be expanded by using your PCI Express slots. Each M.2 expansion card takes up one PCIe slot and can support one solid-state drive. These expansion cards generally use four-lane PCI Express slots, which should not interfere with your graphics card usage unless you run out of slots.

To determine how many PCI Express slots you will need to support your SSDs, you need to know how many drives you want and how many M.2 slots you have. Once you account for all other components that will use your PCIe slots, you can subtract the number of M.2 slots your motherboard has from the number of SSDs you want to connect to get to the answer.

Remember that PCI Express slots aren’t necessary to connect solid-state drives. SSDs can also be connected via SATA cables. This interface will work slower, but the attached SSDs will still run much faster than connecting hard disk drives through the same interface. Conversely, if your SATA ports are all used up, PCI Express slots are a great and even superior substitute.

What Other Components Do I Need PCI Express Slots For?

Graphics cards and solid-state drives are the most common components that use the PCI Express interface, but they are not the only ones. Other components are less frequent because simpler versions of their functionality tend to be integrated into your motherboard or other peripherals, not because the interface is not universal.

You will need free PCI Express slots for any expansion cards precisely because the interface is universal. If you work with audio, you may want a sound card, which will need a PCIe slot. You can also use these slots for network cards with superior capabilities to your integrated hardware or USB dongles.


We’ve learned that when asking “how many PCIe slots do I need?” the essential component to consider is the graphics card, which takes up one 16 lane slot. Beyond this, we’ve looked at what PCI Express is used for so you can count up how many of these slots you may need.

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