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Summary

I bought a new motherboard and CPU. Running the PC with the 2x8GB CL14 2133Mhz RAM leads to crashes, but running it with 2x8GB CL15 2400Mhz works fine. RAM sticks are otherwise identical. I'd assume this was a RAM issue, but they all worked perfectly fine before the upgrade and two RAM sticks going bad at the same time is unlikely. What could be causing the crashes?

Relevant Hardware

CPU:    AMD Ryzen 3800X
MOBO:   MSI MAG B550M MORTAR WIFI
4x8GB RAM:
   - 2x CL14 2133Mhz (HX421C14FBK2/16)
   - 2x CL15 2400Mhz (HX424C15FB2K2/16)

full list here: https://pastebin.com/7af4MgDb

Note that both kinds of RAM are listed on MSI website as supported, so that should be fine.

Crashes

The crashes vary and are inconsistent. The surest way to crash is to run memtester, but I've had crashes on startup and sometimes after 5+ min running just firefox. Crashes vary from General Protection Fault (https://pastebin.com/p1zeqEWP), Segfaults and "rcu_sched self-detected stall on CPU" (https://i.stack.imgur.com/yYlTF.jpg)

What I tried so far

  • run all 4 RAM sticks, both "bad" ones, each one alone and run memtester on each. Errors persist on both CL14 ones whether they're used alone or together. CL15 ones work fine.
  • running Memtest86 to confirm this is not a RAM issue. No errors.
  • run memtester on multiple kernels on Debian 10 and Linux Mint Live USB to confirm this is a hardware issue: crashes happen consistently on all systems, so I think we can rule this out.
  • update to newest BIOS: no change.
  • try running newer CL15 on lower frequency, no issue.
  • try running older CL14 ones on higher frequency and 1.35V instead of 1.2V: it doesn't fix the issue.

Questions

  1. What could be the issue? My working theory is some kind of incompatibility (new Ryzen, old RAM?) or a hardware fault caused by the motherboard.
  2. What else can I try to figure this out? Should I return the motherboard or just buy newer RAM?
fatum
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  • Wait, you let memtest86 run for a while ( at least 15 minutes? ) and no errors? Yet the system is still unstable? – psusi Mar 16 '21 at 15:04
  • @psusi Yes, memtest86 ran fine for hours with no errors. Yet booting the system and running memtester can crash it quite consistently. Other workloads have the same effect, so memtester isn't really special in this regard. Plus both older RAM sticks act the same way. That's why I don't think this is a RAM issue. – fatum Mar 16 '21 at 15:18
  • Are both RAM sticks of the same manufacturer? – harrymc Mar 16 '21 at 16:15
  • @harrymc Yes, both sets were bought as 2x8GB kits and both are Kingston HyperX Fury, they're only different in timings and frequency afaict. Detailed comparison here: https://www.kingston.com/datasheets/HX421C14FBk2_16.pdf vs. https://www.kingston.com/datasheets/HX424C15FB2K2_16.pdf – fatum Mar 16 '21 at 16:21
  • The two sets are not identical. Motherboard/RAM compatibility has many more factors than what is listed in the manuals. For example see my answer in the post [What exactly is the cause of RAM incompatibility?](https://superuser.com/questions/1250578/what-exactly-is-the-cause-of-ram-incompatibility) – harrymc Mar 16 '21 at 16:25
  • @harrymc Motherboard claims to support it, though: https://www.msi.com/Motherboard/support/MAG-B550M-MORTAR-WIFI#support-mem-19 (HX421C14FBK2/16), that's why I'm confused by this. And the error persists even if I only use one of them. – fatum Mar 16 '21 at 16:37
  • We cannot help with any trick that will help. All we can conclude is that your motherboard doesn't like this RAM. Ask MSI Support, it is a better address for asking why. – harrymc Mar 16 '21 at 19:59
  • Thank you, I'll try to ask them and update the question with new info. – fatum Mar 16 '21 at 20:21

1 Answers1

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(Author here)

I do not expect for this to ever resolve, so best I can do is to close this down with the info I have.

As best we were able to determine on MSI forums, this is caused by some incompatibility of motherboard and RAM. Less likely Ryzen MMU and RAM. If anyone has any more datapoints, I'll be glad to hear them, but I resolved the issue by buying newer RAM. Everything works fine now. I no longer have necessary hardware to provide more info, so this is all I can do. Thanks to everyone involved.

fatum
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