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

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.