New details on upcoming Ryzen 3000 CPUs with Zen 2 architecture has been leaked. The integrated memory controller is designed, according to information from circles of motherboard manufacturers, for DDR4-3200 JEDEC based. And that is and thus the highest speed according to JEDEC specification. You can advance on that though.

"Leaker" 188 号 aka @ momomo_us confirmed this. The new Zen-2 CPUs codenamed Matisse will officially support DDR4-3200 with an effective clock of 3,200 MHz and 25.6 GB/s per channel. In dual-channel configuration, the data rate increases to 51.2 GB/s. In comparison Intel currently is at JEDEC 2666 MHz for the latest Coffee lake generation.

Current gen Pinnacle Ridge (Ryzen 2000) is specced at a max DDR4-2933. The same goes for the Picasso generation of AMD APUs, which are also marketed as Ryzen 3000, but do not use Zen 2 in 7 nm, but Zen in 12 nm as their architecture (please do keep that in mind). The Ryzen 3000 ecosystem will be supporting 16 GB per RAM/DIMM module and that means a max of 64 GB for the entire system. 

The official RAM JEDEC support stands for the maximum memory clock without overclocking. However with overclocking (OC) Matisse is rumored to be capable of DDR4-4000 or more. A screenshot suggests a higher OC potential with data of maximum DDR4-4400+ at Matisse and only up to DDR4-3466 + at Pinnacle Ridge. Biostar earlier on advertised up to DDR4-4000 on the upcoming motherboard Racing X570GT8 . The MSI X570 Godlike is rumored to support DDR4-4600 + (OC). The new motherboards are expected to Computex. 

Ryzen 3000: Zen-2 CPUs get JEDEC 3200 MHz Specification