It’d be because the 3000 series can support 128GB with double stacked RAM.
Every AM4 Ryzen supports 128 GB total memory with four 32 GB UDIMMs. The only reason that this was not stated in the past is that this requires DRAM chips with 16 Gb dies that only have been available for about a year.
I have been running 128 GB for a little while and haven’t had any stability issues yet.
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Are those the corsair LPX 32GB dimms?
Nope, these are Samsung DIMM 32GB, DDR4-2666, CL19-19-19, ECC (M391A4G43MB1-CTD).
(I have an ECC fetish)
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so udimms and rdimms have the same physical slot compatibility?
These are UDIMMs, not RDIMMs. As mentioned 32 GB per module (without going RDIMM) has only been possible for about a year.
ECC does not automatically mean RDIMM although presently there are no RDIMMs without ECC functionality. Which makes sense since all platforms that handle RDIMMs usually use ECC (And since Intel is sooo concerned about not confusing customers they cut RDIMM support from some socket 2066 non-Xeon CPUs where running RDIMMs had been possible with ECC disabled).
No Ryzen boots with RDIMMs since AMD disabled that feature in the memory controller of that product line to differentiate it from Epyc.
i gotcha… Some of the google results were showing reg dimm… (i assumed rdimm)… So i am an ass now
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Yeah, Samsung could use model numbers that are a liitle easier to differentiate 
Yeah the only way to get those is to order NM-AM4-UxS. Just got my NH-U9S and only has the long ones for AM3/AM4.
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Can any of you install ESXi 6.7 U3 without getting a PSOD on the X470D4U?
Update: BIOS version 3.11 that still seems to be the latest internal lab version also doesn’t fix that behavior.
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Negative I’m only running U2. I don’t have time to dick around with U3 yet I have some car issues that are eating up my spare time.
Did you load it from the image or do it via an update from ssh? I’ve heard the latter has better luck with updates. I would suggest loading U2 and then going to U3.
I also needed to disable a lot of legacy settings in my BIOS just to get U2 to work.
Good luck.
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I’ve tried the current 6.7 U3 setup iso. Will try to get an U2 one.
No word from ASRock Rack so far when a BIOS with AGESA 1003 ABB or newer is really available so the random numbers generator bug would be fixed.
Yesterday they sent a message saying 3.10/3.11 already had AGESA 1003 ABB which is clearly incorrect (Fedora 30 also doesn’t boot).
It seems did not hit this issue because I went with a r7-2700 in my x470d4u MB, I have a 3700x now, but its in a B450M-HDV R4 motherboard.
Availability of this board in Europe has practically disappeared. A few weeks ago there were like 10 vendors who sold the board. Yesterday it was 3, today there is 1 (probably not current). I wonder if the source has stopped selling them due to high rates of return or if they’re waiting for an updated version. Anyway, something seems to have changed, at least in Europe.
@ aBav.Normie-Pleb, how to overclock your memory? I got my 4 of M391A4G43MB1-CTDQ today, and they are default running at 2400
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
My four M391A4G43MB1-CTD get automatically set to DDR4-2400 after a CMOS Reset or “Auto” settings, too.
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thanks for your detailed explanation
Just wondering what those cost you found some for like $250
Since they became available again In Germany late July the lowest price is around EUR 196 apiece (including sales taxes).
Still haven’t had any stability issues with them but I am really pissed that ASRock Rack hasn’t released a BIOS with AGESA 1003 ABB yet since I initially bought the X40D4U/3700X for the potential use with ESXi and now I can’t do anything but wait for ASRock Rack to make a move.
I’m even doubly pissed that they have ceased replying to found issues/bugs since late July/early August.
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PSA: BIOS 3.20 has been released.
https://www.asrockrack.com/general/productdetail.asp?Model=X470D4U#Download
- Update Console Redirection function
- Improve M.2 compatibility
- Update Secure Boot
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