Just a little update on the new build with the 3990X and Cinebench scores. It can barely finish sometimes at 4.40GHz all-core, but it's unstable, let alone sustainable in a closed case (BeQuiet Dark Base Pro 900 Rev.1 non-window). I always really enjoy finetuning systems. I often see people buying the highest-end hardware which have all bells and whistles for maximum performance, to then run them at stock or perhaps a profile like XMP (which often doesn't properly work). Here are my results of a day's testing:
CPU: Stock
Mem: 3400 (1:1 FCLK)
CB23: 52.500
CPU: Stock
Mem: 3000 (1867 FCLK)
CB23: 53.250
CPU: Stock
Mem: 3733C18 (1:1 FCLK)
CB23: 54.500
CPU: Stock
Mem: 3733C16 (1:1 FCLK)
CB23: >54.500 (CL has little influence on CB23)
CPU: 4000MHz @ 1.2V (still testing this setting, it seems mainainable at around 85-90c equilibrium).
Mem: 3733C16 (1:1 FCLK)
CB23: 70.500
CPU: 4375MHz (1.400V)
Mem: 3733C16 (1:1 FCLK)
CB23: 71.750
This is on Windows for easier and quicker benchmarking, and with SMT disabled (due to macOS compatibility).
Main issue arising was the X.M.P profile not working at all (partially due to subtimings, and the FCLK not supporing 1900MHz). Need 1.25V on SOC and some 1.4V on the memory to get to said frequencies. It's four out of eight sticks, and dual-rank. There are many memory settings to focus on regarding stability. Techpowerup has a great roundup, here. The FCLK 1867MHz clock seems a hard limit, as I get Error Code 07 if I go at 1900 or over. Let's not forget it's Zen2. VDDP at 1100mV and VDDG's at 1050mV.
All this under two 360mm rads, D5 pump, and nine case fans (BeQuiet! and Noiseblockers). Ah, and, pushing 4.40GHz @ 1.4V actually draws around 1000W system power, which is my PSU's spec, so in order to go further a bigger PSU would be needed. The 4.0GHz @ 1.2V stays nicely within this budget, allowing for a ~250W-ish GPU.