Most people know PCIe as the slot used to install their graphics card, and nothing more. It's the long horizontal receptacle located beneath the CPU socket that has duplicates below it (similar-sized or smaller), which are mostly ignored. Among these "other" PCIe slots are a few PCIe x1 slots that might appear too small to be of any real use. However, these tiny slots are probably the ones that are the most versatile. On a modern motherboard, you may not feel the need to add any expansion card, but older motherboards can benefit from advanced NICs, extra USB and SATA ports, and discrete sound cards. If you're an enthusiast, even your modern motherboard's PCIe x1 slots can allow you to expand its capabilities, thereby avoiding investment in a new motherboard.

Most people only ever use the primary x16 slot

Your graphics card isn't the only thing that uses PCIe slots

Unless you're a power user who populates almost all their motherboard slots, runs an elaborate home lab, or uses two GPUs together, you've probably never used any other PCIe slot except the primary x16 slot. The other x16 slots, which often run at x8 or lower speeds, depending on the chipset, are there to accommodate additional graphics cards, SSD adapters, or HBA cards. The higher bandwidth of these additional slots makes them pretty useful for the right user, but most people never need these high-performance expansion cards. Gamers, professionals, and regular users usually have all the expansion slots, connectivity features, and audio capabilities they'll need built into the motherboard itself.

I've used PCs for over 25 years and yet never populated anything other than the primary PCIe slot on my primary machine. Of course, I've experimented with expansion cards on my secondary builds once they became slightly outdated, but most of my time has been spent on my primary build. And while PCIe expansion cards could have enhanced my main PC's feature set, my use case could never take advantage of, say, an advanced NIC or sound card. That said, if you feel limited by your motherboard's ports and slots, it may be time to use your unused PCIe slots.

Your PCIe x1 slots can fill in the gaps left by the motherboard

Don't rush to buy a new motherboard

If you have a slightly older motherboard with Gigabit or even 2.5GbE LAN, you may be aiming for something higher on your next build. Fortunately, you don't need to wait that long to enjoy greater bandwidth for your NAS or home server. A 5Gb Ethernet card can instantly upgrade your PC's networking chops, removing a major bottleneck for your file transfers, backups, and parallel VMs. And the 8 Gbps bandwidth of even a PCIe 3.0 x1 slot is more than enough to sustain the 5 Gbps needed for the NIC. If you wish to jump to 10GbE instead, you'll need a PCIe 4.0 x1 slot at least.

If you're running out of USB or SATA ports instead, you can use PCIe adapters to introduce extra ports so you no longer need to remove some devices when plugging in others. Most budget motherboards never provide enough USB or SATA ports, making the life of a power user quite difficult. Instead of switching to a better motherboard, you can buy economical PCIe adapters that only need the bandwidth of a PCIe x1 slot.

Then, there are capture cards or sound cards you can install in your PCIe x1 slots if you need dedicated media capture or DAC capabilities. Motherboard audio has come a long way, but it's still not better than a dedicated audio card. If you're worried about using too many PCIe lanes and interfering with the performance of your GPU or NVMe SSD, you'd be relieved to know that your PCIe x1 slots are linked directly to the chipset, using dedicated lanes instead of sharing the ones coming from the CPU.

PCIe x1 is not always about bandwidth

Sometimes, it's just about access

PCIe x1 slots may not enjoy tons of bandwidth, but they don't really need to. The expansion cards that you'd usually install in them often don't saturate the slot's theoretical bandwidth. Whether you're installing a network card, USB card, or sound card, you aren't limited in terms of the maximum speed. The objective of using a PCIe x1 slot is almost always connectivity instead of performance. You're either trying to bypass a motherboard limitation or upgrading a key element of the system without investing in a new board. The bandwidth of an x1 port may be lower than x2, X8, or x16 ports, but it's still enough to fulfill your expansion plans.

Many people ignore their additional PCIe slots, often buying external adapters powered via slower USB ports. A PCIe adapter will almost always provide faster speeds for the same job. The smallest PCIe ports on your motherboard are one of the most useful ways to build on your PC's capabilities. Of course, you should have a genuine reason to do so; otherwise, you're just filling all your motherboard slots just for the heck of it.

Don't underestimate your PCIe x1 slots

Your motherboard's smallest PCIe slot packs in a surprising amount of bandwidth for advanced networking, USB, SATA, and audio cards. Whether your motherboard is too old or otherwise limited, you can enhance its capabilities with cheap expansion cards instead of buying a whole new motherboard. For high-performance devices like NVMe and HBA cards, you're better off using PCIe x8 slots instead.