Hi, I just can't figure it out. I seem to have bandwidth similar to 3000mhz kits. (Benchmark link at the bottom)

My setup is 8700k, z370 Aorus 7, G.skill 2x8 4133mHz 19-19-19-39 Samsung B-die.

XMP is enabled. Manually running at 3800mHz. DDR voltage 1.35V, VCCIO and VCCSA both at 1.25V

My system isn't stable when I increase frequency or lower CL. When I first got the kit and enabled XMP, I had absolutely awful performance (15MB/s read/write) and many crashes. Setting the tertiaries to 7-4-7-7 made XMP automatically drop to 3733 but increased the performance to 50MB/s which is actually HIGHER than what I currently have with 3800mHz. (Link at bottom)

Things I've successfully done:

• Set Frequency to 3800
• Set tRFC to 324 (180ns) ( performance)
• Set tFAW to 28 (no change)
• Set CR to 1 ( performance)

Things I've reverted:

• Set tRRDS tRRDL tFAW to 6-6-24: I lost a little performance and RTL D1's went from 65-66 to 65-74 which apparently means instability. (-performance, instability?)
• Set tWRWR_dr/dd to 7-7: They already seem to be 7 at auto in bios but turn to 9 when I boot. When I tried 7, performance went down. Forgot to check RTL and IO-L. (-performance, instability?)
• Set frequency to 3866: It used to crash like once a month, almost stable but now I've been running 3800 for about a year with no crashes.

Things I failed at doing:

• Set tRAS to 40 because apparently the formula is tCL tRP 2=tRAS, 19 19 2=40. It automatically reverted to 39 when I set it to 40. The kit comes with 19-19-19-39 default XMP.

• Set tWR to 16, it reverts it and I can't find tWRPRE to change it.

Here are my timings and benchmark results in Windows

Here are my BIOS settings, some are different to what ASROCK Timing Configurator reports.

Benchmark from a year ago where I actually had more performance with everything auto 3733mhz tertiaries at 7-4-7-7(Actually 7-4-16-16 for some reason but I'm sure I set them to 7)

Thanks a lot for any help, I can provide any more info if needed. I tried to give as much detail as possible.

Edit:Tried lowering to 3733 again but got even worse results. Edit2:Had to reset CMOS, updated to latest BIOS. Increasing VCCSA and VCCIO to 1.28 seems to increase score.