I recently upgraded my system from 16 GB (two 8 GB sticks) to 32 GB (adding two more 8 GB sticks), and they're all the same brand and capacity (DDR4). The BIOS detects all of them correctly, and Memtest86+ also recognizes the full amount. However, the system only shows 16 GB usable in Linux Mint, and running memtest shows that only 16 GB were actually tested. I've tried reseating the RAM and have made no other changes besides keeping the default BIOS settings. Initially, the RAM seemed to work, but I experienced stuttering and crashes. I've since reseated everything and adjusted the settings to 1866 but am still unsure if things are fully resolved. Any advice would be great!
3 Answers
You might want to check if all RAM sticks are compatible with your motherboard. Sometimes, motherboards struggle with four DIMMs if they aren't specifically supported. Also, have you explored older threads about similar issues? They can often provide insight that leads to a solution!
Memtest errors aren't good news. Try testing each RAM stick one by one to find any defective ones. If they work individually, consider whether any settings in the UEFI might be causing trouble. Some motherboards have issues with all four DIMMs when overclocking settings are enabled, so it might be worth disabling those for a bit.
Make sure you also test with XMP settings turned off. Some motherboards can be fussy when running all slots at higher speeds.
Turning off XMP might help stabilize things. It can sometimes lead to issues with all slots filled, so try running your memory at standard settings and see if that makes a difference.
I’m only seeing options for Auto or a specific profile in XMP. I tested both, but neither solved the problem.

I've booted each stick alone, and they work fine. I even experimented with tweaking the speed and voltage, but it still only registers as 16 GB together.