I really didn't expect this to work. I was playing around with RX/TX DFE Taps and some Impendences, trying to stabilize CL34 8200, so decided to go for 8400 out of curiosity, with 105BCLK, loosened every timing possible, switched my ProcODT to 40 Ohms from 26.7 Ohms and set both RX/TX DFE Taps to 2 Taps to stabilize training. This is definitely not stable in the slightest, especially on the 7800X3D, since BCLK hurts this CPUs stability, due to the limited amount of VCore and VDDIO voltages, but at least I know this board can handle 8400 with the right settings and voltages. I'm upgrading to the 9800X3D or the upcoming 9850X3D in a few months, so I'm going to see if 8400 will be possible from there.
RAM: Corsair Vengeance (CMH32GX5M2B6400Z30) binned for CL30-40-40-104 6400 1.40V EXPO (Hynix A-Die). The weird part about this kit is that it doesn't show up on any motherboard QVL, despite it being manufactured in February 2025. It had no reviews on amazon or any store, so as far as I know, I'm the only one that has posted any screenshots or benchmark performances with this kit.