[Tuna-Fish]

You want to ideally have exactly one DIMM per channel. How many dimms this means depends on configuration, but modern EPYC platforms are 12-channel, so there is likely one slot per channel on your board.

[Two4]

You can run two DIMMs per channel without much downside. There's a dual-socketed server mobo out there that has 48 DIMM slots, making it possible to run 24TB of RAM in a 2U rack-mount

[piperswe]

On current AMD processors, there is absolutely downside to running two DIMMs per channel. That's the discussion we're having here.