Memtest86 does not go beyond "getting memory controller details"

[CFG278]

Since a couple of days I have kernel panics with a brand new iMac 2020 (64 GB RAM) running macOS Big Sur. To rule out if the RAM is defective, I wanted to run Memtest86 from the USB stick. Unfortunately, the boot process does not go beyond "getting memory controller details". The process gets stuck. Is there something I can do?

Thanx,
Gerson Nerger (CFG27

[David (PassMark)]

Sounds similar to this issue, which we had thought was a one off issue.

Can you post the debug log from MemTest86
https://www.memtest86.com/tech_debug-logs.html

[CFG278]

Sure ...

Gerson Nerger (CFG27 MemTest86.log

[David (PassMark)]

Can you open 'blacklist.cfg' with a text editor under EFI/BOOT/ of the USB flash drive and replace the text content of that file with the content in this post:
https://forums.passmark.com/memtest8...9159#post49159

[Eddie750]

I too am having this exact same problem on my new 2020 iMac 10-core i9 w/128GB RAM. Except here is my situation: My 2-month old iMac came with macOS Catalina. Memtest86 worked perfectly to diagnose two of the four sticks of RAM (purchased from OWC).

While the two faulty sticks of RAM were being exchanged, I ran my iMac with 72GB of RAM using the existing 2x32GB OWC RAM, and the original 8GB of Apple RAM that came with my system when purchased. Memtest86 worked perfectly in this configuration.

It was during this time I upgraded my new iMac to BigSur.

The remaining two sticks of RAM arrived. I installed them to bring my system back up to 128GB.

When I run Memtest86, the screen freezes at the exact same location "getting memory controller details".

Memtest will halt at this point now regardless of how much RAM is in my machine, even with only the original 8GB of RAM.

The only difference between before and now, is that I upgraded to BigSur. Nothing more.

Is it possible upgrading my iMac to BigSur somehow prevents Memtest from working? Any ideas would be greatly appreciated.

[David (PassMark)]

According to the internet, they updated the BIOS firmware during the BigSur update, and inserted a few new bugs. Seems they also broke Bootcamp Win10 booting when using a eGPU and bricking some other Mac models. So looks like they also broke MemTest86.

Can you try the blacklist change above. If that doesn't fix it can you post the MemTest86 log file.

Update 21/Dec/2020: We received a response from Apple saying that they found and addressed a BIOS issue that locked up MemTest86. It should roll out in early 2021 (maybe as part of their 11.2 release).

[CFG278]

Can you open 'blacklist.cfg' with a text editor under EFI/BOOT/ of the USB flash drive and replace the text content of that file with the content in this post:
https://forums.passmark.com/memtest8...9159#post49159

Unfortunately memtest86 stops at the same position after exchanging the text. MemTest86.log.zip

[Eddie750]

According to the internet, they updated the BIOS firmware during the BigSur update, and inserted a few new bugs. Seems they also broke Bootcamp Win10 booting when using a eGPU and bricking some other Mac models. So looks like they also broke MemTest86.

Can you try the blacklist change above. If that doesn't fix it can you post the MemTest86 log file.

I made the blacklist changes. Memtest86 still freezes at the same spot. It was certainly worth the try!

[keith]

Thanks for the logs.

It looks like we need to add an extra line to the blacklist (for your iMac model).

Can you add the following to blacklist.cfg, and run MemTest86 again

"Mac-AF89B6D9451A490B",ALL,EXACT,DISABLE_MP

[Eddie750]

Thanks for the logs.

It looks like we need to add an extra line to the blacklist (for your iMac model).

Can you add the following to blacklist.cfg, and run MemTest86 again

"Mac-AF89B6D9451A490B",ALL,EXACT,DISABLE_MP

That worked!! Thank you very much!

[David (PassMark)]

Kind of sad, as the implication is that Apple inserted new bugs in the UEFI BIOS on pretty much all their machines.

We are going to release a V9 beta release of MemTest86 soon. This will contain all the blacklist changes above.

[Eddie750]

Kind of sad, as the implication is that Apple inserted new bugs in the UEFI BIOS on pretty much all their machines.

We are going to release a V9 beta release of MemTest86 soon. This will contain all the blacklist changes above.

Is there a possibility of informing Apple of your findings?

I left Memtest running on my iMac all last night. While it only got to pass 2, it did it without finding any RAM errors, whereas my first time, it found errors within 5 minutes of running the test. Thanks for your assistance! I hope Apple resolves these issues!

[David (PassMark)]

Apple didn't bother answering last time we reported an issue.
Too big to care.

[CFG278]

Thanks for the logs.

It looks like we need to add an extra line to the blacklist (for your iMac model).

Can you add the following to blacklist.cfg, and run MemTest86 again

"Mac-AF89B6D9451A490B",ALL,EXACT,DISABLE_MP

Works for me, too ...

[Eddie750]

I just thought that I would chime in here to say that there seems to be a problem with RAM sold by OWC and installed in the 2020 10-core i9 iMacs. I used Memtest86 to determine two of my four 32GB OWC RAM sticks were faulty. The replacement (and all four) RAM sticks passed fine via Memtest86. My iMac was still crashing. I replaced the 128GB of OWC RAM with 128GB of Micron RAM (via Crucial). All problems disappeared, along with an unexpected bonus of my 2020 iMac running about 20F-degrees cooler.

Even though Memtest86 did not find any problems with my 128GB OWC RAM (after the 2nd RAM replacement) there is something about OWC RAM not working well with these new iMacs that Apple/OWC is not being up front about.