A look at the BIOS
The BIOS we used for the test is an earlier BIOS. The screen shots below is from F4b which looks alike.
The MIT page is where most of the action takes place. EZ Overclock tuner basically allows you to select a range of frequencies you want to overclock the DDR4.
As for Ryzen 2nd generation, the official supported DDR4 has been raised from DDR4-2667 to DDR4-2933. For Ryzen 7 1800X, depending on motherboards and DDR XMP profiles, some users were unable to run DDR4-3200. DDR4-2933 was supposedly stable but not official spec speed.
As for this new generation, we see that the G.Skill memory stocks allows DDR4-3400 C16. It is thus give us some sort of assurance that DDR4-3400 will work properly although the official memory speed is now raised to DDR4-2933. (do take note your experience might differ and you might need to manually tune your ram timings to suit DDR4-3400 or higher).
The CPU Clock ratio is the CPU multiplier. Although XFR2 works on the CPU/board, it might be interesting to see how far this processors can be pushed before they throttle down in speed due to heat.