PC can't post after xmp enabled or manual OC of RAM

Eddy Potter · 11 Dec 2020 at 18:06

Hi there, so, i decided to upgrade my 16Gb pc to 48Gb. My setup is:

ASRock Fatal1ty Z170 Gaming K6
16Gb ram from GEIL (3000Mhz CL15)
i7-6700k
GTX 1070
New RAM: 2 * Kingston HyperX Fury DDR4 RGB 16GB (1x16GB) DDR4-3000MHz CL15 (Model: HX430C15FB3A/16)

So, in order to avoid any "bottleneck" I decided to buy 3000Mhz and CL15 ram. Since the mobo has a 64GB RAM limit, I bought 2*16GB (midterm upgrade to a future 4*16Gb setup).

The RAM arrived and when I inserted it to the slots, the PC had instantly problems booting (appearing, according to Dr Debug from the mobo, problems detecting RAM). I went to BIOS, disabled XMP, restarted and everything worked fine. But if I turn that option on again the PC won't post...

I thought it could be some compatibility issues (there shouldn't be any tho) so I took the old ram sticks and left only the new 2*16. Still the same problem... Tried to deactivate XMP and manually OC the ram, setting it to 3000Mhz (and increasing voltage from 1.2 to 1.35 -> i think this is necessary for the OC, not really sure if anything else, never, until this day, done this before) but the PC still won't post and have problems detecting the RAM... Wondered if it could be a ram stick issue, so I tried all this with each one individually (of the new ones) and still the same problem...

At this moment I'm running 48Gb at 2400Mhz since I'm not using XMP, it drops to its native speed. The old one is 2133 the new one is 2400, and I'm able to manually OC all RAM to 2400 [the new RAM base frequency] but if I surpass that value, the issues reappear.

Any idea of what it might be and how to fix it? Even if not through XMP but by manually OC? I would like to be able to run them all at 3000Mhz

Tetras · 11 Dec 2020 at 18:28

Have you tried setting it to 2666 or 2933 at 1.35?

Eddy Potter · 11 Dec 2020 at 18:33

2933 I tried and still didn't work. 2666 with XMP deactivated I didn't try, but that frequency is an XMP profile of this ram, which also didn't work :/
Anything above 2400 "breaks" the ram, i tried 2500 and it crashed. I can't really grasp how can the ram work perfectly fine, but if I increase its frequency (well within its supposed base frequency) it stops working. And if I restart it via mobo sometimes and get into windows it will be at 2400 (the native frequency).

Tetras · 11 Dec 2020 at 19:05

It could be related to use of 4 sticks, especially mismatched sticks, since the XMP profiles can be too aggressive. Mismatched sticks often need looser timings.

I'm not familiar with OC for Z170, but there might be something you could change to help, like change command rate to 2T.

Eddy Potter · 11 Dec 2020 at 19:53

Tetras said:
It could be related to use of 4 sticks, especially mismatched sticks

When I began to "debug" why it was crashing the entire system, I removed all "old" sticks and when it still didn't work, I remove 1 at a time, to test each on of the new sticks (to check if it could be one of them was damaged from factory) but it still dint work :/. So their problem isnt compatibility issues with the other sticks, but with the system (mobo, cpu, no clue with what it may be) that is not letting them reach the 3000Mhz frequency (even tho the system works fine with that frequency since it was the frequency of the older sticks with XMP enabled)