Question PC will boot with any 1 ram stick, but not both. Suspect the Mobo?

[Spii]

Mobo: Asus Prime Z690-P Wifi
CPU: i7-12700k
PSU: EVGA SuperNOVA 1000 P6
Memory: 2x16 Kingston Fury Beast DDR5 4800 CL38
GPU: (disconnected) EVGA hybrid RTX 3080
SSD: 2TB 980 Pro
Windows 11

I purchased this motherboard exactly 1 year ago when I built this system. I was able to initially post the system with both memory modules in slots a2 and b2, however only with the RAM set at 4000MHz CL38 in the BIOS. I did not attempt to push the modules any further at that time (just really wanted things to work and it was "good enough").

Earlier today I attempted to apply the XMP 1 profile. The system would not start (black screen, no signal, fans still running, no beeps). It would also not shut down unless power was held for several seconds.

To troubleshoot I performed the following steps: I removed all peripherals and the GPU, reset the CMOS with the jumper pins, removed the CMOS button battery for 1 hour and replaced it with a brand new one, and removed then checked the CPU socket for bent pins, and reseated it properly (none were bent - it's also somewhat mesmerizing to look at nicely aligned pins haha).

Finally I pulled one RAM stick from b2 and left one stick in a2. Everything worked normally! I replaced the stick in a2 with the other stick - this worked as well. Hmmm... I tried switching the sticks in the slots and everything stopped working again.

This leads me to believe one of two things: either the CPU memory channels are partially fried (I feel like this is extremely unlikely given it performs perfectly fine in all respects without issue in all slots - just 1 at a time), or the z690's memory controller is partially fried (this seems much more likely to me given its inability to post at the rated RAM speed with compatible modules for over a year).

I've contacted ASUS about the mobo, but am I possible assessing this scenario incorrectly? (i.e. is it much more likely the CPU is the culprit)

 

[Lutfij]

While you're working with one stick of ram, try and get into BIOS and see what BIOS version you're on at this moment of time?

 

[Spii]

While you're working with one stick of ram, try and get into BIOS and see what BIOS version you're on at this moment of time?

Since I cleared the CMOS I thought it would revert to the oldest version? I show it as ver. 0404

Looks like that's the factory default. I'll try updating it.

 

[Lutfij]

Clearing CMOS will only clear prior settings in BIOS. It's good practice since a BIOS update can happen while having latent BIOS settings from the prior BIOS version.

 

[Spii]

Clearing CMOS will only clear prior settings in BIOS. It's good practice since a BIOS update can happen while having latent BIOS settings from the prior BIOS version.

Alright so, updated the BIOS successfully to 2404. 1 stick seems to be working still. I just enabled XMP1 and that worked with one stick (first time I've ever been able to get XMP working!). I'm going to try to put the 2nd stick in and will report back.

 

[Spii]

Clearing CMOS will only clear prior settings in BIOS. It's good practice since a BIOS update can happen while having latent BIOS settings from the prior BIOS version.

Ugh... 1 stick regardless of which stick or slot worked just great - even with XMP turned on after updating the BIOS.

2 sticks together in a2 b2 (or a1 b1 which I also tried for giggles) results in the original issue: black screen, fans spinning, no post, unresponsive machine.

Just returned to 1 stick and it works again immediately... I forgot to mention that I ran an OCCT stability test (default 30 min) and no errors or issues. Running another one now just to see what's what.

Edit: stress tests came back fine on the cpu and the memory. No errors. I gotta believe this is the Mobo...

 

[Spii]

ASUS got back to me and told me to basically do everything I already did except they also asked me to try a new CPU lol

Ya know, because everyone just has a pile of spare 12th Gens laying around to test with! Unbelievable.

Guess I'll start looking for a cheap used i3 somewhere that I can throw away or resell when I'm done.

 

[Spii]

Clearing CMOS will only clear prior settings in BIOS. It's good practice since a BIOS update can happen while having latent BIOS settings from the prior BIOS version.

I just slapped in a new i7 I got locally that I could return if needed and... Everything now works. Including XMP at the rated speed for both sticks.

So does this mean my IMC took a crap on the old i7 or was defective to begin with? I barely ran the thing for more than a year on stock levels and had absolutely no issues with it otherwise.

Something just doesn't seem right and I'm wondering if the budget mobo I'm using is exacerbating what would otherwise not be problems.

 

[Spii]

For anyone wondering: the issue was probably both the motherboard and CPU. I ended up getting a new MB and the issue persisted with the old CPU though I was able to get all the XMP profiles working on one stick with the new MB.

In the end, a new motherboard and new CPU fixed it all. So essentially I lost the silicon lottery with a failing IMC on the chip that crapped out after a year... probably exacerbated from a budget motherboard's cheap-ish VRM setup.

Ugh. $600 later