I installed memtest86+ from the Debian stable repositories; I'm using stretch/stable. However, when I select any of its options from the boot menu, I just get a black screen.
I have not added new memory to the system; I'm planning to, however, which is why I installed the programs.
How do I debug/fix this? I'm not sure where, if anywhere, it stores its log files, and I have the same problem if I install memtest86 instead of memtest86+.
Remark that "memtest86+" is not the same as "memtest86" (https://en.wikipedia.org/wiki/Memtest86).
It has no support for DDR4 memory (yet?). Maybe your PC has that kind of memory? It's around since 2014.
If you have DDR3 or below, memtest86+ should work.
But you presumably need to set your BIOS to boot in CSM (Compatibility Support Mode, legacy mode), because memtest86+ is 16 bit software and cannot support UEFI (https://askubuntu.com/questions/917961/can-i-boot-memtest86-if-im-using-uefi).
On my PC, debian did not install a legacy boot loader, only UEFI, so I cannot reach GRUB when using CSM, therefore I also cannot boot memtest86(+) when installed from debian repository.
At this time at debian buster, the supplied version of memtest86 is 4.3.7, which is very old, doesn't support DDR4 and also seems not to support UEFI. The project is not GPL licensed since version 5.0, so newer versions are not in debian repos.
Maybe the best solution is to create a USB stick with the UEFI booting free version of memtest86 (not "+"), which also supports DDR4.
It's not so sad because memtest ought to ignore your whole operating system anyway :)
