What is PCIe 4.0 & Should You Upgrade Your System?
- PCIe 4.0 is widely used in modern computers, connecting components like GPUs, CPUs, and NVMe SSDs. It supports high data transfer rates and backward compatibility with earlier PCIe versions.
- PCIe 4.0 offers high bandwidth, scalability, and future-proofing. It can transfer 16 GT/s per lane, with slots supporting configurations like x1, x4, x8, and x16. Future versions like PCIe 5.0 and 6.0 promise even higher speeds.
- PCIe 4.0 SSDs can reach speeds up to 8 GB/s with a 4-lane setup. For GPUs, the difference between PCIe 4.0 and 3.0 is usually small. Using multiple NVMe SSDs might saturate the chipset bandwidth, affecting system performance.
In late 2011, PCI-SIG introduced initial specifications for the PCIe 4.0 standard, which was said to offer 16 GT/s or 32 GB/s in a 16-lane setup. The official launch took almost 6 years, and in June 2017, PCI-SIG formally detailed the final specifications of PCIe 4.0.
AMD was the first consumer chip maker to launch CPUs with support for PCIe 4.0, starting with Zen2 and the X570E flagship chipset in 2019. Intel was a bit late to the party, introducing PCIe 4.0 with Tiger Lake the following year.
PCIe 4.0 adopts a 128b/130b encoding technique to transform 128-bit data into 130 bits. This results in nearly 98.46% efficiency, which is much more efficient than previous iterations.
↪ Impact on SSDs and GPUs
In terms of real-world performance, a 4-lane PCIe 4.0 link for SSDs maxes out at roughly 8 GB/s. This is in line with what most high-end consumer PCIe 4.0 SSDs provide, such as the Samsung 990 PRO and WD Black SN850X.
Most GPUs feature an x8 or x16 bus interface, which is ample even for older PCIe versions. However, an outlier is the Radeon RX 6500 XT, which features a limited x4 interface. If your PC uses PCIe 3.0 for the first x16 slot, your bandwidth will be limited to just 4 GB/s with the RX 6500 XT. This results in a performance delta of almost 70% in certain titles between PCIe 4.0 and PCIe 3.0.
Apart from that, you could miss out on a few frames with an x8/x16 card. Unless you built your PC a while back, you are likely to have PCIe 4.0, as it was introduced with Rocket Lake-S (11th Gen) for Intel and Zen2 (Ryzen 3000) for AMD, though you’ll need a B550 or X570 at minimum.
Fear, Uncertainty, and Doubt
It only took a few years for the market to see a sudden shift from PCIe 4.0 to PCIe 5.0 equipped systems. CPU manufacturers are slowly introducing more PCIe 5.0 slots with newer chipsets. Moreover, SSDs faster than 8 GB/s are technologically limited by the PCIe 4.0 standard. So, is it time to upgrade?
Generally speaking, all modern GPUs support no higher than PCIe Gen 4.0. You might expect a significant performance gap between PCIe 4.0 and PCIe 3.0, but that is not the case.
Gamer’s Nexus conducted testing and found that despite the 2x bandwidth difference, the FPS improved marginally by only 2-3% between Gen 3 and Gen 4. Needless to say, PCIe Gen 5.0 will be an even smaller improvement.
Likewise, in the SSD department, the first argument is that PCIe 5.0 supported SSDs are costly. At equivalent capacities, Gen 5 SSDs are almost 2x more expensive than Gen 4 SSDs. Secondly, the speed improvement is marginal since PCIe 5.0 technology hasn’t reached its true potential yet. You’d be paying 2x more for 1.5-1.6x more speeds (upwards of 12000 MB/s).
Lastly, PCIe 5.0 SSDs run extremely hot. You almost always require a heatsink or even active cooling to maintain sustained peak performance. Unless your workload can actually utilize this level of bandwidth, it is not worth the investment.
↪ Potential Benefit of Upgrading
However, a strong point in favor of PCIe 5.0 is that some of Intel’s upcoming Z890 boards are rumored to feature an x8 PCIe 5.0 slot (equivalent to x16 PCIe 4.0 for 32 GB/s) for the GPU. This leaves behind 3 x4 PCIe 5.0 slots for SSDs, directly to the CPU, along with another x4 PCIe 4.0 slot. So, you get the best of both worlds while supplying more than enough bandwidth to the GPU.
Do note that this is just a rumor, and not all of the high-end Z890 motherboards will support this configuration.
The takeaway is that any modern system should be equipped with at least one x16 PCIe 4.0 slot, with the additional x4 based on either PCIe 4.0 or PCIe 3.0, depending on your board model. In light of these facts, it can be easily said that you must upgrade your system based on the CPU, GPU, and other components, not the PCIe generation.
Older GPUs on PCIe 3.0 PCs may not see a huge bump in performance even if upgraded to PCIe 4.0. The same can also be said for GPUs nowadays, though funnily enough, no GPU supports PCIe 5.0 yet. If you’re on a budget, then PCIe 4.0/3.0 will do just fine.
However, if you want a high-end system, upcoming chipsets can quite effectively give you many storage options (3 x4 PCIe 5.0 + 1 x4 PCIe 4.0), with ample bandwidth for the GPU, though you’ll need a PCIe 5.0 (x8) GPU, which as of now, does not exist. This is because the RTX 4090 will run at PCIe 4.0 x8 (16 GB/s, equivalent to PCIe 3.0 x16) speeds since it only supports PCIe 4.0.
