PCIe4.0

EVERYTHING YOU NEED TO KNOW, FROM CAVEATS TO COMPATIBILITY TO SPECS

AMD’S NEW RYZEN PLATFORM USHERS IN THE FIRST BIG CHANGES TO PCIE SINCE 2010.

- Gordon Mah Ung

Come July, AMD gets to hoist the trophy in the race to the next-generation PCIe 4.0 interface for desktop PCs. By combining its upcoming Ryzen 3000 CPUs, Radeon RX 5700 graphics, X570 chipset, and a new spate of PCIe 4.0 SSDs, consumers will be able to build or buy the first PCIe 4.0-based PC.

PCIe 4.0 sounds exciting—it’s the first big change to the interface since 2010. But as always, the questions of who can get it (and who can’t), and who really needs it, are more nuanced than you’d think. Keep reading to get the all the details.

WHAT IS PCIE 4.0?

PCIe 4.0 is the next iteration of the PCIe interface. It’s used for connecting add-in cards and M.2 drives, as well as interconnecting various chips inside a PC. Compared to its predecessor PCIe 3.0, PCIe 4.0 essentially doubles the overall throughput. The chart below from PCI-SIG lays it all out nicely:

If that looks like a boatload of bandwidth, it is. Seizing an opportunity to troll Intel and Nvidia, AMD ran Futuremark’s unreleased PCIe feature test to show how a Ryzen 7 3800X coupled with a Radeon RX 5700 in PCIe 4.0 mode offered 69 percent more PCIe throughput performance than a Core i9-9900K and GeForce RTX 2080 Ti.

REALITY VS. HYPE

One problem with AMD’s demonstration, however, is that “69 percent” performance, while most likely real, probably doesn’t actually translate into more practical gaming performance today. That’s because few games ever saturate the 32GBps of data today’s x16 PCIe 3.0 slot can carry.

This disparity between demand and supply has been proven out many times over the years. Alienware’s laptops actually limit the slot to x8 PCIe 3.0, siphoning off the rest to support the external graphics port. The reason? It doesn’t matter (much).

STORAGE