[Tuna-Fish]

New with DDR5, and it's the reason no-one should consider upgrading memory by adding additional sticks on DDR5 platform -- instead, if you need more memory, you should replace your modules. The additional two slots are basically a newbie trap.

Next gen will do away with this because it moves to CAMM2 and there will only be a single connector on consumer motherboards.

[flemhans]

I'm buying a server with 12 slots, should I go for 4x128 gb instead of 8x64 then?

[Tepix]

No, you want to utilize the extra memory bandwidth of the EPYC server CPUs. Use all 12 channels!

The desktop CPUs only have two memory channels so you don't get a performance benefit by using four memory modules.

[flemhans]

Thanks, I'll try and populate it fully!

[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.

[Numerlor]

Is the server using udimms or rdimms? With rdimms the additional memory controller load from more dimms isn't nearly as much as with udimms