You get more bandwidth by having all memory channels populated. When you have multiple slots per channel, filling all slots at best gets you a few percent bette

You get more bandwidth by having all memory channels populated. When you have multiple slots per channel, filling all slots at best gets you a few percent better memory performance due to having more ranks of memory, but for DDR5 platforms the extra load on the memory controller due to multiple DIMMs per channel brings a big hit to the (officially supported) memory clock speeds. The fastest memory configs for a desktop currently are using one single-rank module per channel. Using one dual-rank module per channel doubles the capacity for typically a slight performance penalty.