System booth with 1 DDR5 in B2, but not A2/B2

Hi !

I got a brand new B650M PRO RS WIFI with AMD 7900X5D and two sticks of DDR5 6000.

When I plug only one RAM in B2 slot, the system boots.
When I plug both my RAM in the expected A2+B2 slots, the system doesn't boot (black screen) and two of the POST RED LED are on : CPU & RAM.
Each RAM stick work individually in B2.
I also tried to upgrade the BIOS with the USB flash to latest (v2.10).

What are the possible causes? My guess is either

- CPU is broken (memory controller?)
- Motherboard is broken

Is there any other possibility? Also what is the most likely?

Thanks!

Hi !

Yes I waited several minutes. I had read in the manual the hundreds of seconds to wait depending on memory size. I have 16GB. Although the manual should be improved. They should write what to expect during this waiting time (a black screen or ?). I will try the memory training options (not sure what the default of "Automatic" means), I wasn't aware of this option, thanks!

Memory part number: FF3D532G6000HC30DC01
Memory part name: Team T-Force Delta RGB 32GB (2 x 16GB) 288-Pin PC RAM DDR5 6000

Note that I found that if I put the two sticks in B1 & B2, it boots. But the system is unstable though. It crashed twice in this configuration. I'm back to running the system in B2 only

I ordered a new CPU and new motherboard. Still curious what are the possible cause in order or probability. Could it be the memory? I read that someone had same problem and swapped to an ASUS mobo and things worked flawlessly.

Thanks,
Francois

Note it was the motherboard. I replaced the motherboard with a new one and now it works.

In retrospect it could have been either of the three (motherboard, RAM or CPU). No way to tell without swapping/testing with known good hardware as far as I know.

(Can't edit the previous reply.)
Was this addressed in an update of the BIOS btw?
I am here because of an Amazon review with a similar issue, claiming only the A2 slot works for him, and that there have been "100s of people reporting it on ASRock's tutorial video, forums". At least the latter part seems exaggerated, as I couldn't find any other thread than this, and I doubt there are 100 individual comments under a video saying the same.