there is no xmmp auto configuration in BIOS in these motherboards,

So to set the correct memory speed do the following:

In BIOS there are 2 separate ways to get to the memory settings.

Although these 2 ways should lead to the very same “folders” and settings, changes done via the first way don’t show up if you access the settings via the second way.

I don’t know if this is really necessary but I use both ways, one after the other and change the “same” settings to the very same values each time.

First way:

BIOS -> Advanced -> AMD CBS -> UMC Common Options -> DDR4 Common Options -> DRAM Timing Configuration -> (Accept the risks to access menu) -> Memory Clock Speed: From “Auto” to 1333MHz for DDR4-2666, for example.

Second way:

BIOS -> Advanced -> AMD Overclocking -> (Accept the risks to access menu) -> DDR and Infinity Fabric Frequency/Timings -> DDR Frequency and Timings -> DRAM Timing Configuration

When you are in BIOS also set the amd precision boost to enable for extra benefirt.