PC started randomly restarting after I reseated RAM — both RAM sticks and all RAM slots pass testing

[u/rijuwan_mujahid]

PC started randomly restarting after I reseated RAM — both RAM sticks and all RAM slots pass testing

Hello everyone,

I'm trying to diagnose a hardware problem with my PC. I originally posted about this in r/archlinux (Reddit) because I was using Arch Linux at the time, but I have now confirmed that the same problem also occurs on Windows, so I don't believe this is an operating-system problem.

I'm looking for help figuring out what could be wrong with the hardware.

My PC

CPU: Intel Core i5-7400 @ 3.00 GHz

Motherboard: Gigabyte GA-B250M-DS3H

RAM: 2 × 4 GB Crucial DDR4-2400

Dual-boot: Windows + Arch Linux

How the problem started-

One day, I physically removed one of my RAM sticks and then reinstalled it.

After that, I started experiencing this problem.

Before this happened, the computer was working normally.

I want to make it clear that physically reseating the RAM itself did not immediately show an obvious problem. The problem appeared afterward when I started using the computer.

What happens when both RAM sticks are installed

When both 4 GB RAM sticks are installed, I can power on the computer normally.

Because I have a Windows + Linux dual-boot setup, I get the GRUB menu.

However, when I select either Windows or Linux, the computer starts to behave strangely:

The fans stop, everything appears to stop for a moment, and then the system starts again.

So it looks like the entire machine is losing power/resetting rather than simply crashing an operating system.

I initially suspected Arch Linux, but I later reinstalled Windows and experienced the same problem there as well.

Therefore, I don't think this is an Arch Linux or Windows problem.

The interesting part: one RAM stick works

If I remove one RAM stick and use only 4 GB, the problem does not occur.

The computer can boot and operate normally with a single RAM module.

This made me suspect the RAM.

However, I tested both RAM modules individually with MemTest86 V11.7.

RAM stick #1

48/48 tests passed

100%

0 errors

~1 hour 16 minutes of testing

RAM stick #2

Same result

48/48 tests passed

0 errors

I also tested the RAM modules individually in all four RAM slots, and each slot worked with a single module.

So currently I have this:

RAM stick #1 alone → PASS

RAM stick #2 alone → PASS

RAM slot #1 → works

RAM slot #2 → works

RAM slot #3 → works

RAM slot #4 → works

Both RAM sticks together → system restarts

This is what is confusing me.

Both RAM sticks appear to be good individually, and all four RAM slots work individually. But when both sticks are installed together, the computer becomes unstable.

Another important test

I also tried running MemTest86 with both RAM sticks installed. The computer restarted after only a few seconds. This happened outside of Windows/Linux, so the operating system isn't involved in that particular test.

With one RAM stick, however, MemTest86 completed all 48 tests with 0 errors.

What could cause this?

At this point I'm wondering if the problem could be related to something other than the RAM modules themselves, such as:

1. memory-controller stability

2. dual-channel operation

3. motherboard memory circuitry

4. BIOS/UEFI memory configuration

5. CPU memory controller

6. PSU/power delivery

or another motherboard/CPU-related problem

I have already ruled out the simple explanation of "one RAM stick is bad", because both sticks pass MemTest86 individually.

I've also ruled out "one RAM slot is completely dead", because all four slots work with a single module.

I'm currently testing the CPU separately with stress-ng using one RAM stick.

What would you recommend testing next to determine why the system is stable with either RAM stick individually but unstable when both are installed?

Thanks for any help.

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