2 DIMMS : - B2 + A1 = NOOK (C5) - B2 + A2 = NOOK (C5) - B2 + B1 = OK (no DDR though, since it's the same bank... and seems unable to work at frenquencies > DDR5-3600...)
Same results with the Kingston kit or the G.Skill kit, or mixing both kits for 2 DIMMS tests. Also conducted the 1 DIMM tests with both DIMMs from each set, just to rule out a faulty one.
So, it looks like A bank is not working at all (power works tho since RGB lights up).
The CPU seems fine : video output is working, and the stress tests under windows (when the system booted with a single DIMM) passed.
I did reseat the CPU multiple times, and carefully inspected both the CPU and the socket : no damage, or any sign of contamination. Inspected the every single DIMM slot too, no visible issue either.
The cooler is not too tight (and never was).
I don't have a spare 7xxx CPU to test the board with another CPU.
What is C5 Q-Code ? (since it's not in the manual) Does it pinpoint the cause with any certainty ?
Could it be BIOS related ? (with the latest updates pushed to avoid "burning" 7xxx3D CPUs and limiting SoC voltage ?) Should I try to flash older BIOSes then try and conduct the same tests all over again ?