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MemTest64 causes instabilities

tj91

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I've been testing my new system for a few days, now. I'm running the Ryzen 3600 processor on an Asus Crosshair 6 Hero (x370) mainboard, BIOS version 7106 and 32 GB RAM (Crucial Ballistix LT Sport Red, 2 x 16 GB Dual Rank, 3200 MHz XMP).

When running MemTest64, my system usually becomes unstable. Programs just dont work correctly anymore and the system does not recover. Screens might become black, too. In contrast to <this thread here>, I've only allocated 8 out of 12 threads and only around 80% RAM. So it can't be the problem that Windows runs out of memory completely. Unless it's a weird fragmentation issue with the Windows scheduler/allocator.

I first thought my RAM is defective, but ruled that out. All other stress tests and memory test tools worked without any problem so far. To be completely honest, I can't exactly remember whether or not I had a freeze/crash/whatever at the beginning where MemTest64 was not involved. However, I'm quite confident now that I only have issues with MemTest64.

<I posted a longer version of this on Reddit>

Initially I Thought it might be a compatibility issue or simply just a BIOS bug since many issues get reported with the new Zen2 BIOS versions.

Now a friend of mine could reproduce the same behaviour with MemTest64 (also running the Asus C6H board but a Ryzen 1800X). His system has been stable for a long time now. So that settles it for me and I have to say that MemTest64 just is not stable.

One thing that I have to add: I've already ran MemTest64 for 8 hours straight, but was not using the computer at that time, mostly. So, MemTest64 only seems to be unstable when other programs are running. Also quite a few times the issues arised when I opened a program and a UAC request was shown to click "yes" or "no". I'd have a black background (instead of the desktop background), and I'd be able to click "yes" but then the system would be in a weird, instable state already.
 

W1zzard

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Don't set it to allocate that much memory. That memory is effectively gone from other applications, so if you have several other apps open they will get paged out to the pagefile = run ULTRA SLOW, this includes the OS

This is expected behavior. MemTest64 doesn't even run with administrative privileges, it has no low-level hardware access, so it can't do anything that makes the system unstable.

Edit: you are running OCCT and MemTest64 at the same time?
 

tj91

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Well I only allocated like 25 GB out of 32 GB. I'd say 7 GB is plenty for Windows to operate. MemTestPro for example doesn't show similar problems when I allocate that amount or even more.

Edit: you are running OCCT and MemTest64 at the same time?
Yes, I wanted to stress my system while testing the memory. However running OCCT is not a necessity to make the system unstable. It's just been fast to trigger it. Sometimes even before I start the stress test, e.g. while starting the program or more specifically while the Windows UAC request asks me if I want to start the program.

In general, if I do tasks (not too heavy on either memory or CPU, considering it's 4 threads and around 7GB of memory left), the system will usually become unstable after a while if MemTest64 is running. Even when the task manager shows 80-90% free memory. For reference, 90% means there is still 3.2GB left.

MemTest64 doesn't even run with administrative privileges, it has no low-level hardware access, so it can't do anything that makes the system unstable.
That's what I thought too, so this is even stranger.

Maybe the following has to do something with it? MemTest64 usually fails to allocate the memory in its first (or second, or third, ...) try, even though there is enough memory left.

Example - imaginary - run:

  1. Around 30 GB free memory
  2. MemTest64 tries to allocate 25GB, fails when it has allocated 8 GB
  3. MemTest64 tries to allocate 25GB, fails when it has allocated 15 GB
  4. MemTest64 tries to allocate 25GB, fails when it has allocated 20 GB
  5. ...
  6. MemTest64 runs.
It's not always like this and it's not always that MemTest64 allocated increasing amounts of RAM with each try. Sometimes it works at its first or second try. I'm not sure if this behaviour is expected and why it is occurring. Maybe this hints to some underlying problem, I don't know.
 

W1zzard

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Check page faults with Task Manager, that shows you when Windows is making use of the page file
 

tj91

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It's not like every page fault automatically is a read/write to the pagefile. However, I think I'm ready to let this rest and am not really looking forward to investigating the issue further.
If you are certain that it's expected behaviour then it might very well be. I was just not experiencing anything like it with e.g. MemTestPro and there always was free memory left for Windows to allocate. That's what keeps me wondering if something else is going on. Maybe the way MemTest64 works is triggering an edge case in Windows - Or it is as you say and it's simply expected behaviour :)

Thanks for your replies.
 
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