PCIe 4 vs PCIe 3: Do you need Gen 4 in 2020?

Since Nvidia’s upcoming RTX 3000 Series Graphics Cards will be using the new PCIe 4.0 interface, many people are skeptical if their old PCIe Gen 3 Motherboards will be a cause of the bottleneck.

PCIe (Peripheral Component Interconnect Express) is a kind of serial interface present on all the modern motherboards. Graphics cards, Storage Devices (NVMe), Capture Cards, and Network Cards are some of the devices that can be interfaced via a PCI Expres slot.

PCIe Gen 4.0 is the latest standard of this widely used interface. While GPUs have taken a fairly long time to make the present generation PCIe slot obsolete, there are a few other peripherals that actually utilize the PCIe slots to their full potential.

So, is it time to say goodbye to the PCIe Gen 3.0 interface? Are we at a point where we need to upgrade to PCIe gen 4.0? Read on to find out.

But for those of you are in a hurry, PCIe 4.0 could result in a minor impact on the performance of flagship GPUs such as GA102 (RTX 3090) and Navi 21 (Big Navi). However, we will have to wait until the launch of these products to be certain. But for most users who will be buying a Mid-range GPU like the RTX 3060, Gen 4 is unlikely to have an impact on the performance.

    Different PCI Express Generations

PCIe Generation Bandwidth
PCIe Gen 1 8 Gbps
PCIe Gen 2 16 Gbps
PCIe Gen 3 32 Gbps
PCIe Gen 4 64 Gbps
PCIe Gen 5 128 Gbps
PCIe Gen 6 256 Gbps

Let us first have a look at the bandwidth of all the generations of PCI express interface.

PCIe buses come in different configurations. Depending on the number of lanes, they can be found in x1, x4, x8, and x16 configuration.

This is nothing but the number of paths through which data can travel. Each lane has a fixed bandwidth. So, a PCIe x16 slot will be as fast as two PCIe x8 slots / four PCIe x4 / sixteen PCIe x1 slots.

Every generation, the speed of the PCIe slot doubles which essentially means that the present gen PCIe x16 is twice as fast as a PCIe x8 slot. All the PCIe generations are also backward compatible.

The speed will be limited by the older gen peripheral but the peripherals with different PCIe slots will still work fine.

Intel and Nvidia have been slow in adapting to PCIe gen 4.0 but AMD processors and GPUs already support the latest PCIe 4.0 standard. Intel’s upcoming 11th Generation Rocket Lake CPUs and Nvidia’s upcoming GPUs based on Ampere architecture will support PCIe 4.0 standard.

    PCIe Gen 4.0 for Gaming

From the gaming perspective, you don’t really need to care about PCIe 4 just yet. The gaming performance of most modern GPUs doesn’t fully saturate the PCI 3 bandwidth as of now. Even loading games on PCIe 4 NVMe drive doesn’t have a noticeable impact compared to Gen 3.

AMD’s current generation GPUs like AMD Radeon RX 5500 XT, RX 5600 XT, RX 5700, and the RX 5700 XT support PCIe 4.0 interface. The upcoming Ampere GPUs (RTX 3000) will be the first Nvidia GPUs supporting it.

Budget GPUs & PCI Express Gen 4

A few months ago, a lot of articles surfaced on the internet claiming that the PCIe 3.0 bottlenecked the performance of AMD Radeon RX 5500 XT.

This happened after a German website tested RX 5500 XT with PCIe 3.0 and PCIe 4.0 and found out that the GPU performed much better with PCIe 4.0. Since the RX 5500 XT has just 4GB of VRAM, when the memory was full, the extra data is stored in RAM.

Having a PCIe 4.0 slot improves the read-write speed significantly which bumps up the performance of graphics cards with 4 GB or lower VRAM.

The technology was exclusive to AMD back then (still is) and only premium motherboards like the X570 supported PCIe 4.0. Considering the fact that RX5500 XT is a budget graphics card, someone who owns one would not be pairing it with a high-end motherboard like X570 (or even a B550).

Spending extra on GPU would be a smarter choice. So, the whole point of RX 5500 XT having PCIe 4.0 support seemed pointless. Things might change and we might see a lot of budget motherboards with PCIe 4.0 interface hitting the market soon.

PCIe 4.0 with Mid-Range and High-End GPUs

A lot of gamers own a mid-range GPU like Nvidia Geforce GTX 1660 Super, RTX 2060, or AMD Radeon RX 5700 XT.

While those who have built a high-end system with Intel Core i7-10700k, i9-10900k, or the AMD Ryzen 9 3950X alongside Nvidia Geforce RTX 2080 Ti or AMD Radeon RX 5700 XT shouldn’t worry much about the PCIe 3.0 hampering their performance even at 1440p or 2160p resolution.

The maximum memory speed of RTX 2080 Ti is 14Gbps. The RTX 2080 Ti can max out its performance at PCIe 3.0 x8 port. The performance improves by a single-digit percentage when connected in a PCIe 3.0 x16 configuration.

Here’s a video by Hardware Unboxed to help you understand how GPUs scaled on PCIe 4.0.

While it may not seem like it but it has already been two years since Nvidia released GPUs based on Turing architecture. The upcoming GPUs based on Ampere architecture are going to be unveiled soon.

Along with AMD’s Zen 3 based Ryzen 4000 desktop processors, their RDNA 2 based GPUs might hit the market by November 2020; just a month or two after the release of Nvidia’s Ampere based GPUs.

Even if Nvidia and AMD decide to do something crazy, there are very low chances that they will still hit the limits of PCIe 3.0 x16 slots anytime soon. So, the best thing is to do right now is to wait for the upcoming GPUs and see if the PCIe bandwidth has any impact on the performance.

Having said that, if you the planning to keep the CPU and motherboard and upgrade GPU in the future, buying a motherboard and CPU with PCIe 4.0 support makes perfect sense and that is what you should be doing as of now.

    PCIe Gen 4 NVMe SSDs

The loading times of games stored on SSDs is significantly less compared to the Hard Drives. The difference gets even more significant in AAA titles like GTA V, Red Dead Redemption 2, The Witcher 3, Shadow of the Tomb Raider, and many other games with notoriously long loading times.

PCIe gen 4.0 based M.2 NVMe SSDs like Corsair Force MP600, Sabrent 1TB Rocket NVMe M.2 SSD, Gigabyte AORUS NVMe Gen4 is available in the market and offer insane read-write speeds. These are the only peripherals that can fully utilize the PCIe gen 4.0’s high bandwidth.

Gen 4 NVMe SSDs

Theoretically, the maximum data transfer rate for SSDs connected to the SATA port is 600 MBps while the current PCIe 4.0 based M.2 NVMe drives can reach up to 5,000 MBps (due to the limitation of the controller).

We have not even hit the limits of the PCIe 4.0 interface yet. The upcoming Samsung 980 Pro NVMe SSD will go up to 7,000 MBps.

The higher transfer rate of PCIe 4.0 based NVMe SSD is noticeable only when copying files from one place to another and that’s it. There is hardly any difference in loading times between SSDs with SATA connectors and SSDs with M.2 NVMe connectors; the same is also true for PCIe 3.0 and PCIe 4.0 based SSDs.

This might be a deal-breaker for many of the gamers. Even if you planning to invest in a costly PCIe Gen 4.0 based M.2 NVMe SSD, better save the extra money and spend it on a stronger GPU instead.

    PCIe Gen 4.0 for Professionals

As mentioned earlier, PCIe 4.0 is twice as fast as PCIe 3.0. The same work which can be done by x16 slots of PCIe 3.0 can be done by 8 slots of PCIe 4.0 leaving the x8 extra slots free.

These extra slots can be used to connect other devices. Imagine being able to connect multiple SSDs in RAID 0 configuration. That would make transferring data blazing fast. All this is a huge deal for content creators, engineers, scientists who can actually make use of it.

Having a high-speed data transfer is crucial for programmers and computer science engineers working in the domain of AI and data science as well. The huge data sets used in training and testing machine learning algorithms need to be stored and fetched repeatedly.

High transfer speeds are necessary when performing complex simulations and many other real-time applications. The applications of high-speed storage can be found in various fields of engineering and healthcare.

PCIe 4.0 M.2 NVMe SSDs can prove to be quite useful in such a scenario. No speed is good enough, there is always a need for higher and higher performance.

While PCIe 4.0 is still far from being used in all the motherboards, PCIe 5.0 was released in May 2020 and PCIe 6.0 is scheduled for release in 2021. There is a lot of time until we get to see these cutting-edge technologies in our computers.

We might support for PCIe 5 with AMD’s Zen 4 CPUs that are expected to come out in late 2021 or early 2022.

    Conclusion

Game sizes will continue to get larger and Artificial Intelligence algorithms will continue to get more complex. There will be an ever-increasing demand for faster data transfer rates.

Faster data transfer rates will ultimately reduce the computation time and pave the way for the development of all the amazing technologies that we are yet to discover.

Newer generations of PCIe interfaces will play a very prominent role in our computers soon.

But for gamers and home users, PCIe 3.0 is far from being obsolete just yet; there is a lot of time before upgrading to PCIe 4.0 becomes imminent.




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