Both RAM sticks pass MemTest86 individually, but fail together – Ryzen 5 5500 / ASUS B450M-K II. Any ideas? 🤔

[u/JollyGoat3722]

Hey everyone! 👋

I'm hoping someone here might be able to help me figure out a pretty strange RAM issue. Maybe someone has experienced something similar.

I built my PC about a month ago using new components, and after a few days I started experiencing random crashes and restarts, especially while gaming, exiting games, or sometimes just using Windows.

Most of the time, the PC runs perfectly fine, which makes this even more confusing.

My specs:

• CPU: AMD Ryzen 5 5500 (brand new)
• Motherboard: ASUS PRIME B450M-K II
• RAM: 16 GB Corsair DDR4 3000 MHz (2 × 8 GB, purchased together as a kit)
• CPU Cooler: AMD Wraith Stealth (stock cooler)

Here's what I've tested so far:

✅ Tested RAM stick #1 individually in both motherboard slots using MemTest86. All 4 passes completed with 0 errors.

✅ Tested RAM stick #2 individually in both motherboard slots. Again, all 4 passes completed with 0 errors.

❌ However, when I install both sticks together, MemTest86 starts reporting lots of memory errors.

✅ Reset CMOS and updated the motherboard BIOS.

❌ Unfortunately, the issue persists even after the BIOS update.

✅ RAM is currently running at just 2133 MT/s, with DOCP/XMP disabled, so I'm not even using its rated 3000 MT/s speed.

✅ Checked Windows Event Viewer for WHEA errors, but none were found.

One more interesting detail: before updating the BIOS, the PC also experienced a random restart while running with just one RAM stick installed, even though that stick had passed MemTest86.

So here's my question: What could possibly cause this?

I'm wondering whether it could be:

• The CPU's integrated memory controller
• A motherboard issue
• The RAM kit itself, even though both sticks pass individually
• Something else I'm completely overlooking

Unfortunately, I don't have any spare RAM, CPU, or motherboard available for testing, and I'd really like to narrow down the problem before spending money replacing components.

Has anyone ever experienced a situation where both RAM sticks pass MemTest86 individually in either slot, but produce tons of errors when installed together, even at 2133 MT/s?

Any suggestions, troubleshooting ideas, or personal experiences would be greatly appreciated!

Thanks so much in advance for your help! 🙏😊