Yea it throttles with avx offsets 0, 1, 2, and 3. I was using cinebench r15 because I was just quickly seeing what the cpu was capable of since i just got it. Haven't even tried an avx workload yet. I wasn't sure what was causing it till i checked hwinfo and that was vmax stress.
Also tried different bios versions. But when I use eleet x1 1.0.6, it ALWAYS does vmax stress throttling. But if oc only done with bios, it sometimes vmax stress throttles. I found a utility that you can disable it, throttlestop, but I didn't want to have to use a program everytime boot.
Ive also not gotten the cpu to do 5.3 all core in cine r15 yet, without going over 1.4v, not sure of daily safe maximum for these cpu's. Also LLC at -50% 1.4v, idle droop is down to 1.38 to 1.388, then on load with r15 it droops down to 1.30 to 1.35 and fluctuates a bit. Seems quite a bit too much droop for the setting. LLC at default, -25%, and -50% all behave the same, with the default and -25% both drooping 60mv.
my z390 dark with 8700k/9900k doesn't droop that much at default and -25%.