PCIe 3.0 vs 2.0 – What’s the Difference and Which Is Better?

There are many differences between PCIe 2.0 and PCIe 3.0, which aren’t as apparent as you think. Therefore, knowing out requires a good knowledge of the matter.

If you don’t know much about PCIe 2.0 or 3.0, you have come to the right article. We will not only look at the differences between PCIe 2.0 and 3.0 in this article, but I will also tell you what they are and which is better.

The primary difference between PCIe 2.0 and PCIe 3.0 is the bandwidth or the data transfer rate. PCIe 2.0 per lane throughput rate is 0.5 GB/s and caps out at 8 GB/s for 16 lanes. Meanwhile, PCIe 3.0 gets 1 GB/s throughput rate on a single PCIe lane and a maximum of 16 GB/s using 16 lanes. The bandwidth doubles from a PCIe 2.0 to a PCIe 3.0 slot.

This is the main difference between PCIe 2.0 and 3.0, and I am sure you might have heard it already. I am more interested in telling you how we arrived at this difference. 

For that, we have to start from the basics to unravel why the PCIe 3.0 vs. PCIe 2.0 debate exists.

You might be wondering why I am telling you what PCIe lanes are. Well, to put it simply, without knowing what the PCIe lanes are, you won’t be able to understand the fundamental difference between PCIe 3.0 vs. PCIe 2.0. 

PCIe lanes are highways that allow data to travel from the expansion card (e.g., the GPU) to the motherboard or the CPU. To know more about this, refer to my article on what PCIe slots are.

The gist is that the PCIe lanes control the data flow and determine each PCIe’s speed. 

You might be thinking, why not have unlimited PCIe lanes? That is, unfortunately, not possible. A typical AMD or Intel motherboard has anywhere from 28 to 20 PCIe lanes, respectively. 

The number of PCIe lanes a motherboard has depends on the CPU and the motherboard chipset. For instance, the Ryzen 9 5900x, a high-end CPU from AMD, has 24 lanes. 

Out of the total PCIe lanes on the motherboard, 16 PCIe lanes are reserved for the GPU, while the others are used for M2 slots, network cards, sound cards, etc. 

If you want to know to how many PCIe lanes does your motherboard have and their configuration, refer to my article on How to check how many PCIe lanes do I have?

Now comes the main part.

I am telling you about the PCIe lanes because the data transmission depends upon the total number of PCIe lanes in a motherboard and the version of the PCIe a motherboard has.

PCIe 3.0 and 2.0 are different versions of the PCIe technology. Therefore, you can say that PCIe 3.0 and 2.0 are closely related. 

Apart from PCIe 3.0 and 2.0, there are other versions of the PCIe technology. They are;

• PCIe 1.0
• PCIe 2.0
• PCIe 3.0
• PCIe 4.0
• PCIe 5.0
• PCIe 6.0 (impending final release)

After PCIe 3.0, three newer PCIe versions were released. PCIe 4.0 and PCIe 5.0 are primarily used today in modern motherboards. 

The PCIe 5.0 is currently available in the newest Intel 13th generation and AMD 7000 series motherboards.

As for PCIe 6.0, it has not been launched yet. Currently, the PCIe 6.0 is in the testing phase and is rumored to launch in 2023 at the earliest. 

The Throughput Rate of the Different Versions of PCIe 

The throughput rate is a technical term used for the transfer rate of the PCIe. The different versions of PCIe talked about above come with different throughput rates.

The following table summarizes the throughput rate of the different versions of the PCIe slot.

The table shows that each newer PCIe version has double the bandwidth of its previous version. 

This increase in bandwidth is needed because as computer technology progress, new innovative components are released. For these new components to work, they need higher bandwidth than their previous version. Hence the PCIe throughput rate has to be increased in these new components to be supported. 

For example, NVMe Gen4 M.2 SSDs have read and write speeds of 4-8 GB/s. To achieve these speeds, they would require PCIe with high bandwidth. Therefore, you can see that NVMe Gen4 M.2 slots are only available on motherboards that support at least PCIe 4.0 technology.  

Not to take away anything from the PCIe 3.0, it is still quite relevant, but that is how the PC hardware industry is currently shaping up. 

Also, from the table, we can see that the bandwidth from PCIe 2.0 to PCIe 3.0 doubles. So, it won’t be wrong to say that you can use an X16 PCIe expansion card designed for PCIe 2.0 on the PCIe x8 slot of the PCIe 3.0. 

Since the bandwidth doubles from PCIe 2.0 to PCIe 3.0, reducing 8 Lanes will result in the same overall bandwidth between the two versions. In doing so, you will get to save 8 PCIe lanes of your motherboard. 

From a practical standpoint, manufacturers can use this tactic to make high-speed devices requiring fewer lanes because each PCIe lane’s speed is faster. 

This results in better efficiency, power consumption, and lower heat generation. Overall, it is of quite the benefit for the motherboard. 

To sum it up, it can be conclusively said that the difference between PCIe 3.0 and PCIe 2.0 is not just based on speed. Still, due to the varying functionality of both versions of PCIe, it has a wider impact.

Before I move to the difference between these two versions, let’s take a look at some of the similarities between them. PCIe 3.0 and PCIe 2.0 have some common similarities, which are as follows:

Physical Size 

The PCIe 3.0 and 2.0 slots share the same size. They also have the same PCIe connector, so one cannot tell apart the PCIe 3.0 and the PCIe 2.0 slot just by looking at them. 

Since both the PCIe 3.0 and PCIe 2.0 share the same design, the expansion cards that fit on PCIe 2.0 will also fit on the PCIe 3.0 slot.

Although the expansion card will fit into the PCIe slot, it will not perform similarly because the PCIe 3.0 slot has more bandwidth than the PCIe 2.0 slot. Only fast expansion cards will be able to take benefit from the higher bandwidth. 

Cross Compatibility 

The PCIe 3.0 and PCIe 2.0 slot is cross-compatible with one another. Having PCIe 3.0 does not mean that PCIe 2.0 expansion cards and devices will not work and vice versa.  

So, a PCIe 3.0 expansion card will work on the PCIe 2.0 expansion card, while the PCIe 2.0 expansion card will work on a PCIe slot. 

While a newer generation expansion card will work on an older generation PCIe slot, some features will be restricted. The same is true if you pair an older generation expansion card to a new generation PCIe slot.

Although PCIe 3.0 and PCIe 2.0 might have some similarities, they have many fundamental differences. Let’s compare them by these fundamental differences. 

PCIe Lane Speeds

The fundamental differentiating factor between the PCIe 3.0 and the 2.0 slot is the speed at which they can transfer data. 

Think of it, had it not been for the higher speed, the PCIe 3.0 would not have been introduced over the PCIe 2.0.

PCIe 2.0 supports a bandwidth of 0.5 GB/s, while PCIe 3.0 supports a bandwidth of 0.985.

Taking into account the x1 slot, PCIe 2.0 supports a bandwidth of 0.5 GB/s per lane, while PCIe 3.0 supports a bandwidth of 0.985 GB/s per lane.

If you observe, you can see that the bandwidth has almost doubled from PCIe 2.0 to PCIe 3.0. This principle still stands true to this day. Each subsequent generation of PCIe has double the bandwidth of the previous generation. 

For example, the newer PCIe 4.0 has double the bandwidth of PCIe 3.0. 

Support for New and Additional Expansion Cards

The PCIe 3.0 supports more expansion cards that PCIe 2.0 did not offer. Although, this is not directly related to the PCIe because other factors also play a role in this. 

Still, though, the PCIe 3.0 version can be used to install an M.2 NVMe SSD storage drive, which takes 4 PCIe lanes. 

The M.2 NVMe SSDs can have read and write speeds up to 4000 MB/s. Therefore, they cannot be used on PCIe 2.0 because that will limit the bandwidth-carrying capacity of the storage drive and result in slower speeds. 

In addition to speed, the size and the lanes a device occupies also can change with each consecutive generation. For instance, an expansion card occupying PCIe 2.0 slot with 8 lanes would perform the same on a PCIe 3.0 slot with 4 lanes. Since the PCIe 3.0 has double the bandwidth of PCIe 2.0. So, having half the lanes doesn’t affect performance.

Encoding Ability 

Encoding is a technique in which data is converted into a readable form. The way information is encoded dramatically affects the total bandwidth of the PCIe. 

PCIe 2.0 uses the old 8b/10b encoding system. This entails that a total of 10 bits are transmitted from the source to the destination, and of the 10 bits, only 8 bits are the data streams, while the 2 bits are overhead. This leads to data losses and is not a very efficient way of encoding. 

The PCIe 3.0 gets the 128b/130b encoding system, which means that out of the total 130 transmissions, 128 are of data, and only 2 are overhead. This is a much more efficient way of encoding data. 

Since the PCIe 3.0 bears minimal data losses, it can achieve much higher bandwidth than the PCIe 2.0 slot. 

Whereas PCIe 2.0 supports a peak transfer rate of 8.0 GB/s, PCIe 3.0, on the other hand, has a transfer rate of 15.74 GB/s. This means that PCIe 3.0 can transfer data faster than PCIe 2.0, which explains its double bandwidth rate.

Lower Power Usage

PCIe 3.0 is much more efficient than PCIe 2.0. It has double the bandwidth of the PCIe 2.0 with only a marginal increase in power consumption (in watts). This results in the PCIe 3.0 being able to transfer more data per unit of time without needing high power usage.

Futureproofing

Although PCIe 2.0 and PCIe 3.0 are compatible with newer generations, that does not mean they both enjoy the same future-proofing support.

If you want to stay afloat with the latest technical developments and keep up with the newest PCIe trends, then you need to have PCIe 3.0 at the bare minimum in your PC. Allow me to explain why. 

The PCIe 3.0 version has a significantly faster throughput rate than the PCIe 2.0 slot. The new devices and PC components that are coming out require a higher transfer data rate. Hence it means that PCIe 3.0 will be relevant for longer than PCIe 2.0.

PCIe 3.0 is much better than its counterpart for gaming, rendering, streaming, and other tasks.

Due to the slow data transfer speeds, PCIe 2.0 will eventually fade out of the PC industry because it will no longer be used. 

PCIe 2.0 is already a bottleneck for the latest expansion cards, and this aging factor will only worsen with time.

Suppose you are considering a PCIe 3.0 motherboard but have not yet bought it. In that case, I recommend ditching the thought altogether and going with a newer PCIe 4.0 or PCIe 5.0 instead. Remember, newer technology is always better in the PC space because it comes with more perks.

The SSD is a fast storage drive that allows for data transfer at a very fast rate. The PCIe 2.0 slot has low bandwidth, so it cannot take full advantage of the SSD storage drive. So, the speed will be limited when using the SSD on PCIe 2.0. 

On the contrary, using the SSD on a PCIe 3.0 will get users the full-speed read and write speed of the SSD. The same is also true for the graphics card. The GPU will not perform at its peak potential when using the graphics card on a PCIe 2.0 slot. Meanwhile, most GPUs can perform optimally on the PCIe 3.0 slot. 

That being said, the latest Nvidia RTX graphics cards and the AMD Radeon 5000, 6000, and 7000 series graphic cards will not perform optimally on either the PCIe 2.0 or the PCIe 3.0 slot. So, if you use either of those graphic cards mentioned above, consider using a PCIe 4.0 motherboard.

The PCIe 3.0 has higher bandwidth compared to PCIe 2.0 slot. The higher bandwidth support unlocks many new possibilities for using PC hardware that can otherwise not be used on a PCIe 2.0 slot. 

Many new PC components, such as an NVMe M.2 SSD, cannot be used on the PCIe 2.0 slot but can be used on the PCIe 3.0 slot. 

The PCIe 3.0 slot is also backward compatible with the PCIe 2.0, so all your existing hardware will work if you upgrade to PCIe 3.0. Therefore, there are many reasons you should upgrade to PCIe 3.0, with few drawbacks to sway the decision. 

The upgrade to PCIe 3.0 is worth it because PCIe 3.0 supports modern PC components compared to the PCIe 2.0 slot. 

The PCIe 2.0 technology is becoming obsolete, and more and more new PC hardware does not come with PCIe 2.0 support. PCIe 3.0 is also fading from use. However, it is supported by modern PC hardware. 

If you can, I would advise skipping PCIe 3.0 and upgrading to PCIe 4.0. However, if that is not an option, upgrading to PCIe 3.0 is still a worthy option compared to PCIe 2.0.

Related Guides

Check out some of our related motherboard buying guides.

• Best Motherboard for Ryzen 5 3600
• Best Motherboard for Ryzen 5 5600X
• Best Motherboard for Ryzen 7 5800X
• Best Motherboard for Ryzen 9 5900X
• Best Motherboard for Gaming
• Best B550 Motherboard

Check out some of the other related motherboard guides.

• When to Upgrade Motherboard?
• What Are PCIe x1 Slots Used For?
• What Does PCIe x16 Mean?
• Does It Matter Which PCIe X16 Slot I Use?
• How to Test Motherboard Without CPU?

By comparing all the differences between PCIe 2.0 and PCIe 2.0, we looked at which PCIe slot is better. 

I think there should be no confusion by knowing that PCIe 3.0 is superior to PCIe 2.0, and given a chance, you should always opt for the former instead of the latter. 

Let’s quickly summarize the reasons which make PCIe 3.0 superior. The PCIe 3.0 offers a higher throughput rate (data transfer rate) which results in almost all expansion cards, like GPUs, Video cards being faster on the PCIe 3.0 than on PCIe 2.0. 

As a result, PCIe 3.0 is also more future-proof than PCIe 2.0; therefore, you won’t need to upgrade a motherboard with PCIe 3.0 as often as the one with PCIe 2.0. Also, PCIe 3.0 consumes less energy, saving some bills in the long run. 

Based on all the above factors, I can distinctively say that the PCIe 3.0 is better than the PCIe 2.0 slot. 

Now, it is time to wrap up the article. Before signing off, let me know which motherboard you use in the comment section below. While you are at it, do mention which PCIe slots it has.