Unstable RAM after 430 BIOS update

[SightUp1]

I have a Z370-F motherboard. I am running BIOS update 420 and my RAM settings where this:

Manual
100:133
4000mhz
1.15 VO & SA
1.35 RAM Voltage

My kit is from G.Skill. F4-4000C18D-16GTZKW
It was 24 hours Memtest stable.

On 430, I cannot get 12 hours without an error.

Here is what I have tried.


Manual
100:133
4000mhz
CL 18-19-19-39-2N
1.125 VO & SA
1.35 RAM Voltage
-Failed about 12 hours in.


Manual
100:133
4000mhz
CL 18-19-19-39-2N
1.5 VO & SA
1.35 RAM Voltage
-Failed about 8 hours in.


Manual
100:133
4000mhz
CL 18-19-19-39-2N
1.5 VO & SA
1.4 RAM Voltage
-Failed about 40 minutes in.


Seems like more voltage I put through it, the more unstable it became on BIOS update 430. I have never seen that before. Now, even as I am typing this on my Surface, I am running XMP, with a few changes, to see if I can get it to pass a 24 hour memtest like I was easily able to do in the previous version of my motherboards BIOS. I am running 2N, stock is auto. IO and SA are set to 1.1. Everything else is XMP.

Odds of it failing, what do you guys think?
Am I forgetting a vital setting to making this work?
What would you recommend next if this fails again?

[Silent_Scone]

I'm assuming the 1.5v on IO and SA rails is a typo? That much voltage will cause irriversable damage to the CPU, including the memory controller.
It's not unusual for memory stability to lessen with more voltage. Stick to no more than 1.35v as an absolute maximum. If still no joy, you may wish to enter sub timings manually for that kit, which can be viewed via applications like AIDA on the SPD tab.

4000Mhz on 4 DIMM boards can still be tough without additional tuning for some CPU. It's always best to opt for a kit one or two notches lower than the maximum validated frequency for optimal results. Lastly, I would consider lowering your sights on length of stability at those frequencies. If you can pass HCI Memtest for 500% coverage, or Google Stress App test for 1 to 2 hours, I would consider that stable enough for most workloads.