Got my 2nd CPU 3930K and a new board RIVE I thought will solve my 32GB problem. Same issue, can't get all 8 sticks detected on this board as well
Best is when I put 7 sticks it will detected all 28GB, but once i put the last stick to dimm A1 I got 24GB only booted, weird thing is I can see all 8 sticks in SPD info in BIOS and CPU-Z.