AMD Confirms Current X470, X370 Motherboards Won't Support PCIe 4.0 For Zen 2

MSI X470 Gaming M7
We've got some bad news for anyone that was hoping to hold on to their AMD 300- or 400-Series motherboard for a little while adopting new Ryzen 3000 Zen 2 processors. Yesterday, we reported that Ryzen 3000 processor will work on X470 and B450 motherboards without any performance penalty, which was definitely good news to hear.

However, we're learning today that we can't say the same for PCIe 4.0 support. There are a number of PCIe 4.0 devices on the way including the Radeon RX 5700 Navi series of graphics cards and SSDs from Corsair and Gigabyte (among others). There was some scuttlebutt in the past few weeks that some existing X470 and X370 motherboards would support PCIe 4.0 with a potential BIOS update; a feature that we thought would we reserved for X570 motherboards. Comments regarding this impending support came from motherboard manufacturers that over-engineered their boards and felt that they would be capable of carrying PCIe 4.0 signals.

Ryzen 3000

Well, you know what they say when you assume things. Robert Hallock, who serves on AMD's technical marketing team, clarified that there will be no PCIe 4.0 support on pre-X570 motherboards. It looks as though AMD will be locking down X470 and X370 motherboards to PCIe Gen 3 specs to ensure reliability and compliance.

"There's no guarantee that older motherboards can reliably run the more stringent signaling requirements of Gen4, and we simply cannot have a mix of 'yes, no, maybe' in the market for all the older motherboards," said Hallock in a reddit post. "The potential for confusion is too high.

"When final BIOSes are released for 3rd Gen Ryzen (AGESA 1000+), Gen4 will not be an option anymore. We wish we could've enabled this backwards, but the risk is too great."

ASUS ROG crosshair viii formula
ASUS ROG Crosshair VIII Formula X570 Motherboard

It appears that board signaling issues could be the cause for AMD's decision to lock PCIe 4.0 support to only X570 motherboards going forward. Interestingly, the reddit thread in which Hallock posted has a lively discussion going back and forth over whether it should be left up to individual board makers to certify the use of PCIe 4.0.

mp600 ssd connector 2

One redditor, Parad1gm5h1f7, seems incredibly irked with the situation, writing, "Promises made and vendors talking about pci 4 compliance on boards pre x570 release. To me, this reeks of marketing opportunity and purposeful disabling of features to upsell other parts. This is smelling of AMD forgetting what makes them popular and tongue and cheeking customers for profit."

Whatever the case, it seems as though AMD didn't want the blame placed on them if users ran into compatibility problems, which we can totally understand. So yes, PCIe 4 devices will work on older AMD motherboards, but just at PCIe Gen 3 speeds. You can't fault AMD for needing to run these devices in backwards compatibility mode, because when these older motherboards were designed, the PCIe 4.0 interface ecosystem wasn't even in production yet. Tell us what you think about AMD's decision in the comments section.

Updated 6/3/2019 @ 4:26pm
A previous version of this article had factual errors that have been since corrected.