USB Boot Issue - New Mac Mini 2018

[dduncs]

Hi, I'm wondering if someone might be able to help me troubleshoot my issue...

I am trying to run MemTest86 v8 on my new Mac Mini 2018 with MacOS Mojave v10.14.2 installed. I downloaded MemTest86 v8 Free Edition and created a USB boot disk following the included instructions. I restarted my computer and I held down the option (alt) key to attempt to boot from the USB with MemTest86. However after I selected to boot from the USB, I got the Apple logo boot screen for a minute before I was sent to a grey screen (which looked very similar to Recovery Mode) and a prompt to enter the password for my Macintosh HD. After entering my password into the prompt, my computer rebooted from the startup disk (Macintosh HD) instead of booting from the MemTest86 USB.

I should also probably mention that for a very brief second while I had the Apple logo boot screen (before I was sent to the grey screen) a red square quickly flashed behind the Apple logo.

I'm not exactly sure what's going on here, and I'm not extremely tech savvy. I assumed that my new computer with the latest operating system would be able to boot from the MemTest86 USB, but from what I can tell, it's just not using the USB to boot. Would someone please be able to help me troubleshoot this issue? I'd like to test to my new RAM as soon as possible. Any help is greatly appreciated!

Thank you.

-David

[keith]

Could it be related to the new T2 Security Chips on the Mac Mini 2018:

[dduncs]

Hi keith , so it looks like the T2 Security Chip was the issue! In order to bypass it, I booted into Recovery Mode and then changed the Startup Security Utility options to "No Security" and "Allow booting from external media". After I changed the settings and tried booting from the USB, it worked!

Now, I have run into the issue that tinus ran into where the test gets hung up on Test 2. I have opened the cfg file and entered the line of text you suggested. Will share results in the other post. Thanks again for your help!