I’ve decided to provide some recommendations on DDR4 limitations concerning AM4 currently.
As it stands the AMD code has restricted RAM tuning options which means many RAM kits at launch will not be compatible. This is the same for our competitors also. What we recommend is the following: If fully populating a system with 4 DIMMs (2DPC), use memory up to a max of 2400MHz. If using 1DPC (2 DIMMs) ensure they are installed in A2/B2 and use memory up to max of 3200MHz.
The indication I have received from HQ is that AMD has focused all their efforts on CPU performance so far and will release updated code in 1~2 months when we expect improved DDR4 compatibility and performance." In short if filling all 4 DIMM's set your speed to 2400MHz and work up from there. If using 2 DIMM's put them in the A2/B2 slots and a max of 3200MHz should be possible.
In our testing only the Crosshair board achieved 3000-3200MHz, the others were in the 2400-2666MHz range.
BIOS updates will come!