AMD Zen 4 Ryzen 7000 Processors May Stumble With Memory Speeds North Of DDR5-6000

ryzen 7000 hero news
If you're reading this, you're probably a PC hardware enthusiast, and if you're a PC hardware enthusiast, there's a strong possibility you've built a Ryzen system recently. AMD's Ryzen processors have become very popular, particularly in the DIY market, and that's despite a couple of quirks you have to be careful of when assembling such a system.

One of those quirks has to do with the chips' memory controller. The Ryzen memory controller shares a clock domain with the Infinity Fabric that connects all of the components on the processor package, and that means that your memory speed directly affects how quickly your CPU's parts can communicate with each other.

amd slide memory overclocking
This slide from AMD covers it pretty well for Zen 3.

It's for that reason that enthusiasts tend to equip Ryzen rigs with super-fast DDR4 memory, but there's a catch. You see, faster isn't always better. The CPU's Infinity Fabric can become unstable if you clock it faster than ~1.8 GHz, so if your memory runs faster than this speed—that's DDR4-3600, because it's Double Data Rate—then the Infinity Fabric normally halves its own clock rate to sync up and maintain stability and reliability.

Outside of tasks that desperately need extreme memory bandwidth (of which there aren't many), this generally results in a loss of performance compared to running DDR4-3600 with a 1:1 ratio between the memory and IF clocks.

Well, according to WCCFTech, AMD's Zen 4-based Ryzen 7000 processors will function in much the same way, albeit with DDR5 memory instead of DDR4. The target clock has changed, of course—instead of 1.8 GHz, it's 3 GHz. That's a good thing, too, because DDR5 memory operates at much higher data rates than DDR4.

corsair vengeance ddr5 whitebackground
You may not want to run this Corsair Vengeance DDR5-6600 at full speed on AM5.

Assuming that info is accurate, DDR5-6000 will be the optimal memory speed for AMD's Ryzen 7000 processors. That may not sound all that impressive compared to some of the memory overclocking results we've seen, but keep in mind that it's still 25% higher than the memory spec for Intel's Alder Lake processors. Indeed, it's almost assuredly higher than AMD's own spec for memory speed on these chips, which will probably be in the neighborhood of 5200 MT/s.

We expect that the Zen 4 processors will actually accept memory clocks much higher than this, but as we explained above, it may not actually be to your benefit to run the memory any faster than 6000 if the CPU has to drop its fabric clock. Of course, we'll need to do our own testing to determine the truth of the matter.