US How PCIe 4.0 and PCIe 5.0 differ
PCIe 4.0 and PCIe 5.0 are successive generations of PCI Express, the serial link that connects graphics cards, NVMe SSDs, network cards and other devices to the processor. Both are defined by PCI-SIG. PCIe 4.0, finalized in 2017, runs at 16 gigatransfers per second (GT/s) per lane. PCIe 5.0, finalized in 2019, doubles that to 32 GT/s.
Each PCIe generation doubles the bandwidth per lane while keeping the same slots and connectors. PCIe 5.0 therefore lets a device use half the lanes for the same speed, or go twice as fast on the same lanes. Today the gain shows most in the fastest NVMe SSDs and network cards; many GPUs and capture cards still run at full speed on PCIe 4.0.
PCIe generations compared
Both generations use the same 128b/130b encoding, so usable bandwidth is close to the raw rate. Figures are for each direction; PCIe links are full duplex, so the same bandwidth flows both ways at once.
| Generation | Year | Rate per lane | x1 | x4 | x16 |
|---|---|---|---|---|---|
| PCIe 3.0 | 2010 | 8 GT/s | About 1 GB/s | About 3.9 GB/s | About 15.8 GB/s |
| PCIe 4.0 | 2017 | 16 GT/s | About 2 GB/s | About 7.9 GB/s | About 31.5 GB/s |
| PCIe 5.0 | 2019 | 32 GT/s | About 3.9 GB/s | About 15.8 GB/s | About 63 GB/s |
| PCIe 6.0 | 2022 | 64 GT/s | About 7.6 GB/s | About 30 GB/s | About 121 GB/s |
PCIe 6.0 changes the signaling to PAM4 and adds forward error correction, but it is only starting to appear in data centre hardware. For edge and embedded systems, the choice today is between PCIe 4.0 and 5.0, with PCIe 3.0 still common on low-power processors.
What the difference means in practice
Doubling the link speed only helps when the device can use it.
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Bandwidth. PCIe 5.0 carries twice the data per lane of PCIe 4.0.
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Lanes. Faster lanes free up slots and lanes for other devices, which matters on processors with a limited lane count.
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Compatibility. Mixed links run at the speed of the older generation, so a PCIe 4.0 card in a PCIe 5.0 slot runs at PCIe 4.0 speed.
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Heat and cost. PCIe 5.0 SSDs run hotter, which matters in fanless systems, and PCIe 5.0 boards need better materials and sometimes retimer chips to keep the signal clean.
SSDs, GPUs and network cards
NVMe SSDs show the clearest gain. PCIe 4.0 x4 drives reach around 7 GB/s in sequential reads, while PCIe 5.0 x4 drives reach around 12 to 14 GB/s. The improvement in everyday random access is smaller, and PCIe 5.0 drives usually need a heatsink to avoid throttling. Our comparison of NVMe vs SATA on M.2 covers the step below, and our white paper on M.2 expansion slots and keys covers PCIe storage and accelerators in industrial systems.
GPUs rarely fill a PCIe 4.0 x16 link during inference, because the model and data stay in the card’s own memory. A PCIe 5.0 GPU in a PCIe 4.0 slot typically loses only a few per cent. The exception is when a card runs on fewer lanes, such as x8 through a riser card, where the faster generation makes up the difference.
Network cards at 100GbE and above, and multi-channel capture cards, are where PCIe 5.0 becomes necessary rather than useful, since their traffic flows across the bus continuously.
How to check what a slot really runs at
A board advertised as PCIe 5.0 rarely runs every slot at PCIe 5.0. Before relying on the headline figure, check these points.
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Processor lanes or chipset lanes. On current Intel desktop and embedded platforms, PCIe 5.0 usually comes only from the processor. Slots and M.2 sockets behind the chipset typically run at PCIe 4.0 or 3.0.
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Electrical width. A full-length x16 slot may be wired as x8 or x4, and sharing lanes between slots can halve them when both are filled.
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Negotiated speed. Once the system is running, Linux reports the live link speed and width in the lspci output, and Windows tools such as HWiNFO show the same.
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Card support. The link trains to the highest generation both ends support, so check the card’s own specification as well as the slot’s.
Choosing a generation for an edge system
The right generation depends on what the system will plug in. For a gateway, HMI or machine controller, PCIe 3.0 or 4.0 is more than enough. For multi-camera AI with a discrete GPU, PCIe 4.0 x16 is usually sufficient, and PCIe 5.0 adds headroom for future cards. For high-speed storage, capture or 100GbE networking, PCIe 5.0 is worth specifying.
In sealed or fanless designs, check the thermal budget before choosing PCIe 5.0 SSDs: they can draw around twice the power of a PCIe 4.0 drive under load. A PCIe 4.0 industrial SSD often delivers more consistent performance in a hot cabinet than a faster drive that throttles.
Our industrial GPU computers and industrial motherboards include PCIe 4.0 and 5.0 platforms.
Quick answers on PCIe 4.0 vs 5.0
PCIe 4.0 and 5.0: common questions
Is PCIe 5.0 backwards compatible?
Yes. A PCIe 5.0 slot accepts PCIe 4.0, 3.0 and older cards, and a PCIe 5.0 card works in an older slot. The link runs at the slower generation’s speed.
Will a PCIe 5.0 GPU work in a PCIe 4.0 slot?
Yes. It runs at PCIe 4.0 speed, which for most GPUs costs only a few per cent of performance, because inference and graphics work stays in the card’s memory.
How much faster is PCIe 5.0 than 4.0?
Twice the bandwidth. Each lane carries about 4 GB/s each way instead of 2 GB/s. Real devices gain less, depending on how much bandwidth they need.
Is PCIe 5.0 worth it?
For fast SSDs and networking, yes. For most GPUs, capture cards and general I/O, PCIe 4.0 is still enough today.
When did PCIe 5.0 come out?
The specification was released in 2019. The first desktop platforms with PCIe 5.0, Intel’s 12th Gen Core, arrived in late 2021.
We fit and configure the GPUs, SSDs and expansion cards in each system as standard, matched to the slots, lanes and thermal budget of the chassis, and check each device runs at its rated link speed before the system ships.