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What is the difference between PCIe Gen 3 and PCIe Gen 4?

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Feb 2023
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PCIe has been the standard interface for connecting high-speed peripheral components to computer motherboards for the past decade. The fourth generation of this interface, PCIe 4.0 standard, was announced in 2017. However, we did not see SSDs or graphics cards using the new tech until Computex 2019. Today, PCIe 4.0 has attracted an upsurge of excitement for this technological innovation whether it be SSDs, GPUs, motherboards or high-powered expansion cards. But what is PCIe Gen 4? We’ll break down the basics.

PCI Express logo
What is PCIe Gen 4?

PCIe Gen 4 is the fourth and latest generation of the PCI Express specification. The successor to PCIe Gen 3, PCIe Gen 4 is the fastest PCIe generation available on the market today.

What does PCIe Gen 4 do?

PCIe Gen 4 allows systems to connect to high-performance PCIe devices such as GPUs and PCIe NVMe SSDs.

Why is PCIe Gen 4 necessary?

Advancement in PCIe technology is necessary to accommodate the growing need for a high-speed data bus that enables increasingly demanding user applications and workloads.

What is the difference between PCIe Gen 3 and PCIe Gen 4?

PCIe Gen 4 doubles the data rate of PCIe Gen 3, allowing PCIe Gen 4 devices to transfer data at much faster speeds. PCIe Gen 3 operates at 8 GT/s (gigatransfers per second) which roughly translates to 1 GB/s per PCIe lane. By comparison, PCIe Gen 4 operates at 16 GT/s, or around 2 GB/s (gigabytes per second) per PCIe lane.

What is the maximum bandwidth of PCIe Gen 4?

To understand the maximum bandwidth of a PCIe Gen 4 device, you must know the number of PCIe lanes that it supports. PCIe devices use “lanes” for transmitting and receiving data, so the more lanes a PCIe device can use, the greater the bandwidth can be. The number of lanes that a PCIe device supports is typically expressed like “x4” for 4 lanes, “x8” for 8 lanes, and so on.

x1x2x4x8x16
PCIe Gen 3 bandwidth 1 GB/s 2 GB/s 4 GB/s 8 GB/s 16 GB/s
PCIe Gen 4 bandwidth 2 GB/s 4 GB/s 8 GB/s 16 GB/s 32 GB/s
Is PCIe Gen 4 backward compatible?

PCIe Gen 4 is backward compatible, so a PCIe Gen 4 device connected to a PCIe Gen 3 system will function normally at PCIe Gen 3 speeds. That means if you purchase a PCIe Gen 4 NVMe SSD today, you can use it immediately in your current system even if it does not support PCIe Gen 4. If you upgrade to a PCIe Gen 4 system in the future, you will unlock the full performance of your PCIe Gen 4 NVMe SSD.

When will PCIe Gen 4 come out?

PCIe Gen 4 is currently under industry adoption and many PCIe Gen 4 products are available on the market today, however, only the latest products will support PCIe Gen 4. Moving forward, PCIe Gen 4 will become the industry standard.

How do I get PCIe Gen 4?

To take advantage of PCIe Gen 4, your CPU, motherboard, and PCIe devices must all support PCIe Gen 4.

What desktop platforms currently support PCIe Gen 4?

Some desktop CPUs and motherboards which support PCIe Gen 4 and are currently shipping include:

  • AMD Ryzen™ 3000 and 5000 series CPUs
  • AMD X570, B550, and TRX40 motherboards
  • Intel® 11th Gen "Rocket Lake" and 12th Gen “Alder Lake” Core CPUs
  • Intel® Z490, Z590, and Z690 motherboards
What is a PCIe NVMe SSD?

PCIe NVMe SSDs are solid state drives that use the high-speed PCIe bus for data transfer as well as the NVMe (Non-Volatile Memory Express) protocol to communicate with the host system. As these drives operate on the PCIe bus, they offer vastly improved bandwidth and quicker response times than SATA SSDs.

Does PCIe Gen 4 make PCIe NVMe SSDs faster?

PCIe Gen 3 was unable to accommodate the full bandwidth of high-speed PCIe NVMe SSDs. This was effectively creating a bottleneck in SSD performance. PCIe Gen 4 solves this performance bottleneck, allowing PCIe NVMe SSDs to read and write data at much faster speeds.

What form factors are used by PCIe NVMe SSDs?

PCIe NVMe SSDs can use various form factors such as add-in card (AIC), M.2, and U.2. Client PCIe NVMe SSDs typically only use the M.2 2280 form factor because its slim design allows it to easily fit into desktop and notebook PCs. Enterprise-class PCIe NVMe SSDs will use all three form factors, with U.2 being the most popular because of its compatibility with server backplanes.

M.2, U.2 and AIC SSD Form factors


Conclusion

PCIe 4.0 platforms allow for more flexibility and available bandwidth. SSDs that utilize a PCIe 4.0 interface are ideal for data-intensive workloads. They load applications and games faster while also optimizing boot load up time. PCIe 4.0 also brings power-saving enhancements, meaning your device runs cooler while consuming less power. With the emergence of more products adopting PCIe 4.0, the decision between PCIe 3.0 and 4.0 is a no-brainer. PCIe 4.0 will be an industry standard before you know it.

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