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All PCIe Slot Types (Thoroughly Explained)

PCIe Slot Types Cover image

There is no way to overlook the fact that PCIe slots are very important to any PC. These slots are where we install our GPU and some other supported components, and while modern motherboards have more than one slot, people normally only use one, the one where the GPU is installed.

But what do these PCIe slots mean, in the first place? That is a question that a lot of people ask, and in this post, we are going to make it clear for those who are confused.

If you have ever wondered about the PCIe slot types, this post is for you since we are going to look into everything you need to know.

What Is PCIe or PCI Express?

The first thing that you need to understand is that PCIe or PCI Express stands for Peripheral Component Interconnect Express; while the name itself is a mouthful, it is actually pretty self-explanatory.

highlighting the pcie slots of motherboard

PCIe has been around for a long, long time. However, over the time, it has seen generational upgrades and improvements. You use these slots to connect graphic cards, storage devices, network cards, and other devices that share the same interface.

What is a PCI Express slot?

A PCI Express or a PCIe slot is simply a slot that is found on the motherboard, it normally is located on the bottom left side of the motherboard, and you get a number of them on a motherboard; this all depends on the CPU lanes.

These slots can go as high as 16GB/s and even offer a hot swapping feature that lets you unplug an old device and plug in a new one without any issues.

What Are the Different PCI Express Formats?

Considering how PCIe has been around since 2003, we have seen a number of generational upgrades, and with each upgrade, we have only seen better and better performance, as well.

close up image of pcie slot of msi board

At the time of writing this, there are currently five generations of PCie, with each generation offering double bandwidth than the last, and enabling better performance, especially for storage devices.

PCIe Slot Sizes: x16 vs x8 vs x4 vs x2 vs x1

Similarly, PCIe slots also come in sizes. You start with PCIe x1, then you go to PCIe x4, then you move to PCIe x8, and then the full-sized slot is the PCIe x16.

Now, if you are wondering what the difference is, here is a small bullet list that is going to help you understand.

  • ‘PCIe x1’ connections have one data lane
  • ‘PCIe x4’ connections have four data lanes
  • ‘PCIe x8’ connections have eight data lanes
  • ‘PCIe x16’ connections have sixteen data lanes

The more data lanes you have, the more bandwidth you can get between the device that is plugged in and the host.

Almost all the modern graphic cards you see use the x16 slot, with other devices using different slots, as well. It all comes down to how much bandwidth is required, in the first place.

PCIe Slot Versions: 5.0 vs 4.0 vs 3.0 vs 2.0 vs 1.0

Now that you know what each slot is capable of, what about the generations that you are getting? We mentioned earlier that currently, consumers have options of up to PCIe 5.0 generation; however, the 6th generation specifications have been confirmed.

For your convenience, we are sharing a table that shows the generations of each slot, as that will give you a better understanding.

PCIe 1.08 GB/s2.5 GT/s2.5 GHz
PCIe 2.016 GB/s5 GT/s5 GHz
PCIe 3.032 GB/s8 GT/s8 GHz
PCIe 4.064 GB/s16 GT/s16 GHz
PCIe 5.0128 GB/s32 GT/s32 GHz
PCIe 6.0256 GB/s64 GT/s32 GHz

As far as the PCI 6.0 generation is concerned, the specs, although are confirmed, we haven’t seen devices running on this generation, but that shouldn’t be far as we might get something later this year, and that would make sense.

PCI vs PCIe: Speed

A lot of people often get confused between the PCI and PCIe and the speed they offer. Well, PCI is offered in either 32 or 64-bit, with 133 MB/s and 266 MB/s speeds, respectively.

However, the PCIe speed is a bit more complicated to understand as it Is still developing. Therefore, when you are trying to figure out the speed of the latter, you have to look at the generation, along with the size of the slot, and then you will have a better understanding as to what you are looking at.

So, before you determine, it is always better to compare slot sizes, as that will give you a better understanding.

PCI vs PCIe: Compatibility

In terms of compatibility, the 32-bit PCI interface cannot run 64-bit interfaces, but it does work vice-versa. As for PCIe, considering how it has different lengths, the longer one can support shorter-length PCIe devices but not the other way around.

They are also backward compatible in terms of the version/generation they are on but will run on the max speed of the previous generation.

So, for instance, if you connect your PCIe 3.0 device to a PCIe 2.0 interface, it will operate at the 2.0 speed.

Last but not the least, PCI and PCIe devices are not cross-compatible with each other, and you cannot go ahead and use the devices on different slots.

What Are The Uses of PCIe Slots?

PCIe slots are used for all sorts of purposes. Simply put, you can just go ahead and connect various devices ranging from your usual graphic cards, storage devices, Wi-Fi cards, capture devices, Bluetooth devices, and more.

detaching graphics card from motherboard

However, considering how most of the features are now built-in inside the modern motherboards, we normally don’t see a lot of other uses. So, you can just go ahead and connect all the relevant devices whenever you want.

However, be sure that you are connecting the right ones and not getting confused with what needs to be connected and what doesn’t.

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– My Final Verdict:

If you are confused about the PCIe and PCI slots, then it is only common because a lot of people find themselves in the same situation.

However, this post is going to clear up things so you really do not have to worry much about the situation you are in. Rest assured; you would be all sorted once you go through all the information.

Frequently Asked Questions

Question 1: Can I put PCIe x4 in the x16 slot?

Yes, this is known as up-plugging, and it is completely possible and compatible without any issues. However, you cannot put the x16 device in an x4 slot due to the size difference.

Question 2: Can I put PCIe x1 in the x16 slot?

Yes, as mentioned before, this is entirely possible thanks to a universal compatibility; however, the compatibility is one-sided and won’t work the other way around.

Question 3: Which PCIe slot is the fastest?

PCIe x16 is the fastest as it offers the most bandwidth and is usually reserved for graphic cards, so they can run at their full potential without any issues coming in the way.

Question 4: What is PCIe x4 slot used for?

The x4 slot is often used for NVMe SSD expansion cards along with RAID controllers, network adapters, and capture cards.

Question 5: Can I put NVMe in PCIe x16?

Yes, you can; however, you might need a PCIe adapter since most NVMe SSDs are available in M.2 form factor. But you do often see some PCIe-based offerings as well.

Question 6: Which is better, PCIe x16 or PCIe x1?

Of course, the PCIe x16 slot is better because of having more bandwidth and generally better overall compatibility with the rest of the devices.

Question 7: Is PCIe 4.0 x4 backward compatible?

Yes, they are backward compatible, but you will be limited to the speeds of an older generation if you go for backward compatibility.

Question 8: Can I use a PCIe 4 GPU in a 3.0 slot?

Yes, you can, but you will be limited in terms of bandwidth. But in the case of GPU, you might not notice the performance difference.

Question 9: Can I put a PCIe 4.0 in a 3.0 slot?

Yes, you can, but as mentioned before, there is a limitation in terms of the performance you get, as PCI 4.0 will run at the max speed of PCI 3.0.

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Furqan Shahid

Furqan Shahid

Reader, writer, and gamer. I started my gaming journey with NES and back then, it was the greatest thing that I had ever put my hands on.

For me, it was the best thing in the world. However, as I progressed into the world of gaming, it soon dawned on me how this rabbit hole is a never-ending one and soon gaming turned from my passion to my profession. I have been gaming for 24 years and have extensive knowledge about not just platforms, but building computers as well.

My Expertise is in Computer hardware, PC Gaming, Video Games, Software and Apps, Computers, and Laptops.

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