Posted on Friday, February 24 2017 @ 15:31 CET by Thomas De Maesschalck
Some more details from the motherboard makers. It could be an incomplete list but the memory compatibility page of the MSI X370 XPOWER Gaming Titanium shows just one 2666MHz kit and one 3200MHz kit, everything else is 2400MHz or below. For comparison, the memory compatibility page of the Z270 XPOWER Gaming Titanium shows many modules with a marketed frequency in excess of 2400MHz.
And then there's also this nugget from the ASRock X370 Taichi manual:
Similarly, the Gigabyte/Aorus AX370-GAMING 5 motherboard that's included with the Ryzen review kit lists compatibility with modules of a speed of up to 3200MHz but if you want to use four modules the maximum seems to be just 2666MHz.
The Biostar X370GT7 memory compatibility page contradicts this as their list includes several modules with a frequency between 2400MHz and 3600MHz, but it does not provide details about two vs four DIMMs.
UPDATE: For clarification, the issues are reportedly more prevalent on the lower-end and mainstream Socket AM4 motherboards but even flagship boards have issues with OCing to DDR4-3600. As such, ASUS recommends users to start at 3200MHz and work your way up from there if you use two memory modules. If you use four DIMMs you're recommended to start at 2400MHz.
The issue is not vendor specific and the wording of the ASUS statement indicates the solution will involve a CPU microcode update from AMD so it is a fixable and relatively minor problem with the processor.
Original post:
Gibbo from OCUK received an update from ASUS that confirms AMD's Ryzen platform has issues with high-frequency DDR4 memory. There were some rumors about this and here we have the first hard confirmation that there's indeed a DDR4 memory compatibility problem.
AMD reportedly focused all its efforts on improving CPU performance and put DDR4 support on the backburner. Motherboard maker ASUS reports you can use DDR4 with a frequency of up to 3200MHz if you populate just two DIMMS on a motherboard, but if you want to use all four DIMMs you can't clock the memory higher than 2400MHz.
This issue is expected to be resolved via a BIOS microcode update for the AMD Ryzen's integrated memory controller, the ETA for this is 1-2 months.
A comment from Asus:
"
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!
