Hi everyone I want to build a AI ML PC I dont want to spend to much I can get a Asus WS C621E Sage + Dual 28-Core Xeon Platinum P-8136 CPU w/ Heatsinks and 384gb Samsung DDR4 2400/2666MHz ECC RDIMM RAM for 1999 $ I was thinking or getting 4x Asus RTX 3090 TUF and then upgrading the ram to Intel Optane 128GB DDR4 PC4-2666 288 DCPMM Persistent Memory NMA1XXD128GPS I can get it cheap at 59 $ and water cooling everything or am I better to just bite the bullet and go new the difference in price if I go new is 5000$ can anyone help me on this please , I know the Asus WS C621E Sage is a fairly old MOBO but I was thinking I could save and still get something decant Thanks in advance
The WS C621E is a single DIMM per channel (1 DPC) board, so remember with Optane you are losing bandwidth because you are replacing DRAM. Optane DCPMM in memory mode converts your DRAM to an L4 cache, so you need at least two DRAM DIMMs per CPU.
I use 4x512GB Optane DCPMM sticks (two per CPU) in my HP Z6 G4 daily driver which is similarly only 1 DPC, and the memory bandwidth decreased significantly. For me, this isn’t an issue because my workloads run in cache, but your mileage may vary.
If you are planning to use these CPUs, remember Optane DCPMM is a Cascade Lake feature (82xx CPUs, not Skylake 81xx CPUs). If you want a good LGA 3647 workstation CPU for cheap with Optane DCPMM support, look into the 6268CL or 8273CL.