What’s the difference – and similarity – between PCIe 3.0 and 2.0?

A computer's PCIe (Peripheral Component Interconnect Express) slots allow you to add extra cards. While they're most commonly associated with adding a graphics/video card to a computer, they have a variety of uses. These days, PCIe can be used for many functions, such as adding a sound card, network card, WIFI card, and more.

However, not all PCIe slots are the same. With technological advancements, PCIe has now progressed to versions 4.0 and 5.0. But today, we'll be discussing the differences and similarities between its previous generations, PCIe 3.0 and 2.0. In this article, we'll delve into their specifics. Let's dive right in.

What is PCIe?

PCIe, short for Peripheral Component Interconnect Express, is a standard bus interface for computer expansion. It is also defined as a serial computer expansion bus, allowing you to connect additional devices to a computer's motherboard.

Typically, PCIe expansion slots are used to add graphics cards, SSD storage devices, Wi-Fi adapters, and other types of expansions. While PCIe is generally faster than its predecessor, PCI, it has also seen various improvements from its earlier versions.

In fact, PCIe 7.0 was announced to be in development as of June 2022. However, we expect this version to become standard only over the next 5-6 years, as the process of going through various reviews typically takes that long.

AMD's Zen 4 processors and Intel's 13th Generation support the latest PCIe version 5.0. However, the most common standard in computers worldwide is still PCIe 3.0.

That brings us to today's topic, the capabilities of PCIe 3.0 and 2.0, which have been the standard for years. It wasn't until the 11th Gen Intel CPUs and AMD Zen 3 that PCIe 4.0 became the standard, which is why PCIe 3.0 and 2.0 are still very relevant today.

PCIe History

PCIe 1.0 was introduced in 2003, with a data transfer rate of 2.5 GT/s per lane. However, each version has differed. It wasn't until 2007 that PCIe 2.0 came along, nearly doubling this rate to 5.0 GT/s per lane.

Then, in 2010, PCIe 3.0 came out with a rating of 8.0 GT/s. That's why it's been the standard for PCIe devices for over a decade. However, before PCIe 3.0 became the standard, PCIe 2.1 was released in 2009.

Though it has the same throughput per lane as its predecessor, it does get a little boost from it. The only improvement that 3.0 has over 2.0 is better support, serial bus management, and troubleshooting capabilities. Still, PCIe 3.0 officially took over from its predecessor in November 2010, providing better speeds and support.

Differences Between PCIe 3.0 and PCIe 2.0

The similarities between PCIe 3.0 and 2.0 are actually quite limited. Their differences mainly stem from their individual development and intended purposes. However, to help you better understand the distinctions, here's a comparison table: | Feature | PCIe 3.0 | PCIe 2.0 | | --- | --- | --- | | Data Transfer Rate | 8 GT/s (64 GB/s per lane in x16 configuration) | 5 GT/s (40 GB/s per lane in x16 configuration) | | Bandwidth | Doubled compared to PCIe 2.0 | Same as PCIe 1.0 | | Cabling | Same physical interface as PCIe 2.0 | Same physical interface as PCIe 1.0 | | Backward Compatibility | Yes, with reduced performance | Yes, with reduced performance | | Latency | Slightly improved due to more efficient encoding | Slightly higher due to 8b/10b encoding | | Power Efficiency | Improved due to more efficient signaling and encoding | Less power-efficient compared to PCIe 3.0 | | Application | Suitable for high-speed devices like NVMe SSDs and high-end GPUs | Originally designed for mainstream storage and GPUs | Please note that this is a simplified comparison, and there might be additional technical nuances not mentioned here. The main takeaway is that PCIe 3.0 offers significantly higher data transfer rates and improved efficiency over PCIe 2.0.

And you can see not only different lanes, but actually different speeds within the same lane, which is why it's important to know about these differences, even though they're all backward-compatible.

However, a PCIe 2.0 card will run at its maximum capability on a PCIe 3.0 slot, not at the speed of the platform.

Similarities Between PCIe 3.0 and 2.0

While they have some differences, they both use the same 1x, 2x, 4x, 8x, and 16x interfaces. However, as mentioned, the main difference lies in their bandwidth speeds.

Again, though, while PCIe 3.0 devices will be backward-compatible with 2.0 slots, their performance will be limited by the older platform's bandwidth.

In contrast, a PCIe 2.0 device is forward-compatible with PCIe 3.0, but it operates only at its own speed.

Frequently Asked Questions (FAQ)

This section will have other common questions about PCIe 3.0 or 2.0, so check here to see if you can find an answer.

1. Will a PCIe 2.0 card work properly in a PCIe 3.0 slot?

Yes, it can. As mentioned earlier, PCIe devices are typically backward and forward compatible. So, any PCIe 2.0 device will work fine in a PCIe 3.0 slot, but it will operate at its maximum speed, not the speed of PCIe 3.0.

Is PCIe 2.0 a bottleneck?

It depends on the device you're using. If you have a PCIe 3.0 or 4.0 card in a PCIe 2.0 slot, it will certainly be a bottleneck. The slot's bandwidth is insufficient to allow the card to operate at full speed.

3. Is PCIe 2.0 compatible with NVMe?

Though PCIe 2.0 doesn't have a direct interface to NVMe or M.2 devices, you can find adapters that let you connect these storage devices in a PCIe 2.0 slot.

4. Is PCIe 3.0 sufficient for gaming?

Considering it is 2022, and the technology was released in 2010, one might say it is outdated. Currently, PCIe 4.0 is standard, with PCIe 5.0 on the horizon. Therefore, an upgrade in 2022 would be more appropriate.