Ah, that explains it. Two works fine, but 4, that’s where the problem starts.
Workstations typically have 128 GB RAM or more so need those 4 slots. All the Mobo makers sell boards with 4 slots, but what they don’t tell customers is “Warning: We haven’t really figured out how to make 4 DIMMs work yet, so only use 2 of the slots!”
I got furious when I delved into that rabbit hole and discovered that there is almost zero support across all motherboard makers for 4-DIMM kits. Parts had already been ordered, delivered and assembled. Buried deep in reddit threads, the ugly truth was revealed. Like a fine-print in a 20 page legal contract, and not a word from AMD on this issue.
AMD really dropped the ball here. Intel knew of the challenges of DDR5 and >2 sticks and that it would take years to hammer out, so adjusted their product plans to support DDR4 for their latest product line to give the workstation customers a workaround. A very responsible decision in my opinion.
AMD’s approach of “sod the customer” and just hiding the issue, I’m not a fan of. Anyone else who thinks about building a 4-DIMM workstation is very likely to run into the same headache.
That said, if you don’t foresee needing more than 64GB RAM within a year or two, then going AMD should be pretty safe.
