Need help ASUS KRPA-U16 + AMD Epyc 7D12 - Weird Memory issues

[LordCharas]

Hey guys new member and first time poster so please let me know if this is not the correct section to start this thread. I am currently trying to put together a server for homelab use.
I have built computers for years but it is my first time using actual server grade hardware so I am hoping it is some BIOS setting and not defective hardware.

Build’s Name: N/A
Operating System/ Storage Platform: Unraid or TrueNAS - not there yet.
CPU: AMD EPYC 7d12 32c/64t
Motherboard: ASUS KRPA-U16
Chassis: N/A
Drives: N/A
RAM: Trying various configurations of 1x8 - 8x8 of Samsung 2666mghz DDR4
Add-in Cards: GT720 just for HDMI video out for now
Power Supply: 550w Bronze rated silverstone (temporary for now)
Other Bits: N/A

I am going based off the manual found here from ASUS section 2.4.2 - https://dlsvr04.asus.com.cn/pub/ASUS/mb/SocketSP3(4094)/KRPA-U16/Manual/E15821_KRPA-U16_UM_WEB.pdf

First problem, the POST screen and BIOS are reporting different amounts of memory installed I wanted to go with the 8x8. The POST screen read 32gb and threw me 4 Dimm timing errors (these slots are for the 2nd set of 4 modules for the 8 dimm config) and it showed 57gb in BIOS - Refer to pictures.

First thought was that one of the memory modules were bad so I began testing with both sets of 4 individually. Individually both sets of 4 showed no POST errors and reported 32gb but still was showing 57gb in the BIOS. I had 2 extra identical modules I mixed them around with the same exact results so I ruled out one of the memory sticks being defective.

Other Trouble shooting I did: Update BIOS, Clear CMOS, Memory check/tests on boot, Disable all RAS settings in BIOS - All still left me in the same place.

I am hoping this is something simple that I may have just overlooked as I am not looking forward to dealing with ebay/seller if this is in fact defective(shipped slow boat from china). This is the bundle that I purchased FYI - ASUS KRPA-U16 + 7D12+4U motherboard+CPU+Radiator supports AMD EPYC7002 PCIE4.0 | eBay

Please let me know if there is any other info I can provide!
Thank you!

 

[ban]

Any luck?

I just bought MZ32-AR0 and 7D12 combo. Your comment is making me nervous lol. My vendor said it was showing the same bogus 57GB in BIOS but didn't mention DIM Timing errors you ran into with U16 board.

According to Gigabyte, Rome uses 8 channel. To use all 16 physical slots over 8 channels. This is what they said
Enabled via BIOS setting (“UMC Common Options” “DDR4 Common Options” Configure “Enforce POR” setting).

Can you see if U16 has this feature? It's under 4.10.3 but I don't see Enforce POR listed. If you do find it, try both combination enable and disable.

 

[ban]

oh I see it now, according to your user manual
Go to 4.10.3. U16 calls this a Power Down Options. Default is AUTO. Disable it. See if the board sees your 4 sticks. If yes, ENABLE it but configure it for using 4 sticks over 2 channels. So move the sticks around. I have DDR3200 registered LRAM at 64GB. I really want to use all 8 slots while fooling the CPU into thinking only 4 were connected. This would be disappointing but I'll be happy regardless if I can get 256GB recognized instead of 512GB.

 

[ban]

PS I bought from the same vendor. Really nice guy. He's very responsive. He recommended me Asus board too but I went with Gigabyte for more PCIe slots. I'm just trying to modernize my stock trading workstation but don't want to waste money on high electricity. MZ32-AR0 + 7D12 makes the most logical choise so I can have more graphic output. They're basic 2D graphics. Nothing fancy. I'm not gaming with this setup. Just trading stock and watching youtube. Man you gotta give me hope please tell me you got U16 + 7D12 booted

 

[ban]

Comon buddy, give me hopes. Move those RAM around into different arrangement. Something gotta work

 

[upalachango]

The 7d12 only has 4 memory channels instead of epyc's normal 8 channels. Half of those slots are going to be disconnected from the CPU so makes sense the mobo reads the memory but can't get the CPU to communicate (the RAM slots can't be dynamically assigned).

I've seen one person claim you can only run a single dimm per channel because of tdp limitations, but I haven't seen anyone else confirm this and it doesn't make a lot of sense that tdp would play a role. I'm looking to build a 7d12 system myself and am a little worried about the RAM situation (probably just over thinking it though).

If you look at the manual for the mobo, it shows that the first 4 channels you should populate are C/D/G/H. Your POST shows A/B/E/F are giving the error and those would require the full 8 channels of a retail Epyc SKU. Pull those sticks and put them into slots C1/D1/G1/H1. If the 7D12 does support two DIMMs per channel, that should work. If it doesn't, you can experiment with a bunch of other combos or take just a 5th stick and put it into each slot at a time to verify if any others are accessible. If nothing works beyond the first 4 in the CDGH channels works, you'd confirm that 7D12 only supports 4 total DIMMs.

I'd greatly appreciate it if you can post a follow up with your findings. There isn't a lot of details on the 7D12 beyond core count, TDP, 4 memory channels, and that it is supported by most SP3 server mobos. I hope you're able to get everything running.

[Edit] the 57344mb reported in the BIOS is 56gb. You likely have one bad stick of memory on top of the inherent CPU limitations. If you go into the memory settings can you see which DIMMs are populated? The BIOS is reading the memory based on what the motherboard can see which will be different from the CPU which will report only what it can see (and hence the errors during POST). If the BIOS shows the status of each DIMM that'll help narrow down which stick is bad. You'll want to remove that first before testing if you can use dual DIMMs with the 7D12.

 

[LordCharas]

Hey sorry guys, I gave up on this for a little bit and didnt follow up with my original post. I will go through these troubleshooting steps and post results. One of my friends just told me the same thing about the CPU being able to handle only 4 Channels. Hopefully it can take the 2dimms per channel at least if that is the case.

I am leaving to visit my parents in a week and that is where I would deploy this to replace the computer that i've been using as my server.
So all troubleshooting will be done before I leave

 

[The man]

Hello everyone, I bought a set of krpa-u16 + 7d12 from Chinese friends. There is practically nothing on the Internet except for this discussion. I bought memory separately - 4 x 64GB Samsung M393A8G40MB2-CVF
I'm trying to start it up - the computer doesn't turn on at all, even the fan in the power supply. Only the stand-by LED is on and the BMC LED on the board is flashing.
I tried to insert one or two slats into different sockets - unsuccessfully.
I will now look for different types of memory to check what the issue is - in memory, or in a board with a processor.
If someone has this set working, write down what kind of memory.
Sorry for the bad English

 

[The man]

for information: it worked in this configuration after clearing the CMOS and reconnecting the power supply. A wonderful set! I'm sorry for distracting everyone.

 

[LordCharas]

Well thank you for all your help gents. I was able to get this board working with the 7D12 as well. @ban I found the settings in BIOS but I did not have enough matching memory sticks to try out if all 16 physical slots will work over only 4 channels. I tried a windows 10 pro install just shits n giggles and it was not successful. Install got stuck on the initial start a few times and the 1 time it went through, windows would not boot. I was able to successfully install and boot into ubuntu. Perhaps windows server edition is needed? not sure on that.

@upalachango Thank you for the detailed response. I moved the sticks over to C/D/G/H and I am able to get 2 DIMMS in each channel. Only loss I see on my end is that I would have just bought 16gb or 32gb sticks to start rather than 8gb with the hopes of using all 16 DIMMS. Any additional memory in any other channel is throwing a DIMM timing error on boot.

Boot screen will recognize the proper amount of memory installed, bios screen is always showing the wrong amount.

Thank you all again, please let me know if any more testing is needed from me. It will be difficult to do so once it's deployed.