- 8 x DDR4 DIMM sockets supporting up to 256 GB (32 GB single DIMM capacity) of system memory
- Quad Channel memory architecture
- Support for DDR4 4400(O.C.) / 4266(O.C.) / 4133(O.C.) / 4000(O.C.) / 3866(O.C.) / 3733(O.C.) / 3600(O.C.) / 3466(O.C.) / 3400(O.C.) / 3333(O.C.) / 3300(O.C.) / 3200 / 2933 / 2667 / 2400 / 2133 MHz memory modules
- Support for ECC Un-buffered DIMM 1Rx8/2Rx8 memory modules
- Support for non-ECC Un-buffered DIMM 1Rx8/2Rx8/1Rx16 memory modules
- Support for Extreme Memory Profile (XMP) memory modules
because it is quad channel you want to populate all 4 channels for maximum performance possible; not populating all 4 channels will still work just not as fast as it could possibly be.
RAM is installed in pairs (i forget that specific reason, its not the "dual data rate DDR" thing though). So 2 x 4channels = 8 total slots. Each slot at most a 32gb dimm, a 64gb dimm will not work. so 32 x 8 = 256gb = max ram supported = maximum performance in terms of both speed and memory capacity. If you did 8x8gb DIMMS for 64gb total ram the performance would be the same just not the capacity (for the same memory speeds).
Maximum performance would be 8x32gb of DDR4 4400, installed in all 8 DIMM slots, followed by DDR4-4266, and so on.
And unbufferred non-ECC ram would be fastest, which is the typical consumer ram; ECC ram (for servers) would technically be slower; if interested a web search on non-ECC vs ECC should answer that in technical terms if you're interested.