Bizarre compatibility issue: PRIME B550M-A WIFI II, Ryzen 7 5700X

[OVERKILL]

My son has an Alienware socket AM4 system w/Ryzen 7 5700X in it that he wanted to migrate to a new Corsair case, so he bought a case, but hadn't realized that the Alienware board had a proprietary back panel, so that took us board shopping. Unfortunately, the case he bought limited him to MicroATX.

Now, the Alienware water cooling setup uses an Intel bolt pattern (as does their board) so he had to order another kit, got a Thermalright setup for it that supports AM4. 

Ordered him the PRIME B550M-A WIFI II, put it all together, no POST. 

Tried a minimal config, still nothing. 

Tried:

-4x different video cards (and two we know worked in the Alienware board)

-2x different sets of RAM, with a single stick tried in every slot

-Re-seated the CPU

-Cleared the CMOS, pulled the battery

Took it all back apart, tested it all in the Alienware board, it worked. 

OK, so, I contacted ASUS through the Chat, they recommended I RMA the board. While I was waiting, I figured I'd order an advanced replacement, which arrived today. 

EXACT same symptoms. 

I cracked open a new PSU (ASUS ROG 850W) and tried that "just in case", still nothing. 

The board powers on, video card fan spins, but USB never initializes. Some quick googling led me to similar symptoms with ancient BIOS versions and incompatible CPU's, but this CPU has been supported since 0303 and both these boards shipped with 3607. 

I've now ordered another CPU to test with, a Ryzen 5 5600XT, just to confirm the board works (which I assume it will), but I have a very hard time with the idea I received two defective boards that exhibit the exact same symptoms. 

Anybody else experience anything like this? 

[Jiaszzz_ASUS]

Hello @OVERKILL 

After verification by the relevant departments, we have confirmed that the Ryzen 7 5700X is able to boot into the BIOS and operating system when using BIOS versions 3607 and 3611:

We recommend cross-testing with another 5700X or different hardware components to further isolate the issue. If the problem persists, please consider whether an RMA service is necessary for further inspection.

Thank you.

[OVERKILL]

I RMA'd it, and included the CPU, so that they could test with the CPU (which, as we've established, works fine in another motherboard with a different chipset). 

However, they did NOT test the CPU in another board, only the board with another CPU (that was NOT a Ryzen 7 5700X), which I had already established, worked, prior to RMA'ing in the board. It was the combo of the two devices: this Ryzen 7 5700X and this B550M chipset motherboard, that seems to produce this issue. 

Interestingly, this is not an issue unique to ASUS, here is somebody having the same issue with the same CPU on an MSI motherboard, also with the B550M chipset:

https://forum-en.msi.com/index.php?threads%2Fproblem-with-msi-b550m-pro-vdh-wifi-motherboard-ryzen-7...

Trying the same CPU in an A520M chipset board, it worked fine for him. Which is what I expected the ASUS RMA department to do, try the included CPU in a different board with a different chipset. 

So, they've sent me a replacement board, but it's still an unworkable combination, which I'm not thrilled about. We know both components work, the issue is that they don't work together. 

[Jiaszzz_ASUS]

Hello @OVERKILL 

As previously mentioned, based on our tests, we did not encounter the issue you described. Since that you have already sent the motherboard for repair and replacement, we recommend continuing to monitor the performance of the returned motherboard with the 5700X installed.
Please ensure proper installation, making sure there are no bent pins and that the CPU is neither too loose nor too tight.
Furthermore, as you mentioned encountering similar issues with other brands, if the problem persists, we recommend considering reaching out to AMD for technical support or a hardware diagnostic for the CPU.

Thank you.

[OVERKILL]

I bought myself the ROG STRIX B550-F motherboard, which has diagnostic LED's on it. It hangs with the DRAM LED illuminated with this 5700X CPU installed. I ordered a 5800XT for myself, which I fully expect to work properly. I've advised my son to just put the 5700X back in the Alienware board and sell it, since it works fine in that board, but none of the 4x ASUS ones we've tried (all B550 chipset mind you). 

As I mentioned, they didn't try this CPU in any other motherboards and it didn't work in the board they returned to me, so there wasn't much troubleshooting done and that whole process wasn't any help. I'm wondering if there is some weird early 5700X compatibility issue with later chipsets, which would also explain the guy with the same CPU and MSI motherboard (same chipset) having the same issue. 

[Jiaszzz_ASUS]

Hello @OVERKILL

I have provided an update regarding your case and repair details via private message. Kindly check it at your convenience. 

Thank you.