Question DIMM slot works with 8GB stick of RAM but not 16GB ?

[Devorient]

I had two CMK32GX4M2E3200C16 (2 x 16GB) RAM sticks installed in my PC with XMP profile active for roughly a year. Suddenly, my PC started crashing and restarting after loading games.

Luckily I had two CMK16GX4M2B3200C16 (2 x 8GB) RAM sticks laying around so I tested the system with them, everything worked fine.

After some more investigation with the help of Windows Memory Diagnostic, I found out that when running with a 16GB RAM stick (regardless of which of the two CMK32GX4M2E3200C16 sticks) installed in DIMM channel A, a hardware fault is detected.

Some of my test results:

Channel A	Channel B	Works?
16 GB	16 GB	No
16 GB	-	No
8 GB	16 GB	Yes
-	16 GB	Yes

So I settled on a working configuration with 24GB RAM for now.
I am somewhat puzzled on where to place the blame and I don't have more parts on hand to test with sadly.
What do you think is the most likely cause of the fault? Any pointer on what I could try next?

Summary from HWiNFO64 (working system)
Computer: GIGABYTE B550I AORUS PRO AX
CPU: AMD Ryzen 5 5600 (Vermeer, VMR-B0)
3500 MHz (35.00x100.0) @ 3593 MHz (36.00x99.8)
Motherboard: GIGABYTE B550I AORUS PRO AX
BIOS: FFa, 07/11/2024
Chipset: AMD B550 (Promontory PROM19 C/C1)
Memory: 24576 MBytes @ 1600 MHz, 16-20-20-38
- 8192 MB PC25600 DDR4 SDRAM - Corsair CMK16GX4M2B3200C16
- 16384 MB PC25600 DDR4 SDRAM - Corsair CMK32GX4M2E3200C16
Graphics: ASUS DUAL GTX 1070
NVIDIA GeForce GTX 1070, 8192 MB GDDR5 SDRAM
Drive: KINGSTON SNV2S1000G, 976.8 GB, NVMe
Drive: ADATA SX8200PNP, 1000.2 GB, NVMe
Sound: NVIDIA GP104 - High Definition Audio Controller
Sound: AMD Family 17h/19h - HD Audio Controller
Network: RealTek Semiconductor RTL8125 Gaming 2.5GbE Family Ethernet Controller
Network: MediaTek RZ608 Wi-Fi 6E 80MHz Wireless Network Adapter
OS: Microsoft Windows 11 Professional (x64) Build 22631.4169 (23H2)

 

[Ralston18]

Doublecheck the Motherboard's User Guide/Manual.

Some motherboards require that the first physically installed RAM be placed in a specific slot.

Commonly DIMMA2.

And also check all of the "fine print" and "Important Notes" etc. often presented within the Memory Installation pages.

 

[Devorient]

Looking though the manual I see that I have not really checked if the memory was supported, sadly for me it is not.
Very similar modules are listed but neither of the two I have are.
Kind of strange for the system to work properly for a year, only to stop working because of that now.
I guess I'll start by getting something supported and see where that leads.
Thanks for the suggestion

 

[Misgar]

I frequently fit RAM that's not in the motherboard QVL and it usually works OK.

Have you booted the PC up from a USB stick and run MemTest86?

If you're going to be thorough, test each DIMM on its own in the first DIMM socket with XMP disabled. Then test the same DIMM in the next socket. Repeat until you have tested all DIMM sockets with the first DIMM.

This should prove if the first DIMM is OK. It will also prove if both memory controller channels A and B are OK. It will also prove if all the DIMM sockets are OK. Write down the results.

Now test the remaining DIMMs, one at a time. You may find that one or more DIMMs have gone bad due to XMP overclocking. You may find that one of your CPU's IMC channels is defective. You may find that one of your DIMM sockets is bad. You could find any combination of these three factors.

Repeat MemTest 86 check, but this time with XMP enabled. This will put more stress on the CPU IMC and the DIMMs, especially if the XMP setting is much higher than the JEDEC default.

You might find that a DIMM that passes MemTest86 at Jedec default speed (either 2133MT/s or 2400MT/s) but fails at XMP overclock speed (3200MT/s).

 

[Devorient]

Thank you for the thorough explanation. I will go through a testing round this weekend.

 

[Devorient]

After a lot of testing, I could not really move any further into understanding why this has happened.
I'll wait until I get my hands on a different motherboard or CPU to investigate this further.
Thanks for your suggestions.