Hey all. I've had the Z390 Dark for a few weeks now and love it. But I'm having a heck of a time getting my memory stable. Can't even run it at rated XMP speeds/timings. 
 
It's this: https://www.gskill.com/en/product/f4-4600c18d-16gtzr
 
My 9900K overclock is rock solid at 5GHz all cores with 1.28 voltage. But unless I run my memory at "auto," I have instability. The Dark states it's compatible with 4600MHz memory and AFAIK, G.Skill makes the only kind on the market, so I'm stumped. Any thoughts?

Meaning that I lost the silicon lottery with my 9900K?

I have the same ram, 9900k, and dark mobo. I have a weird issue. My ram runs near stable at 3900 mhz  15,15,15,36 2T. Not tested much but no bsod. But what ever I do, I can' t make my board post at 4000 mhz. 4000 mhz with even 20 timings not posting. Try sa/io 1.5v, dramv 1.7, 1.8, 1.9 even 2.0 volts. Nothing changes. Increased cpu vcore, no help. What is my problem don' t understand. It s like something directly putting the system into bootloop after 4000 mhz. Possible I am missing something? Or some bios problem?

I, also,  am having issues running G.Skill 4000cl17 1.35v sticks. I can run them at xmp 4266 with 1.45v, only at stock timings though. Using k|ngp|n's setting I can not post unless I slow down to 1800Mhz. The lowest I can go in timing is 16-16-16-36 without the system going into the circle of doom. I just assumed that I could go really low timings and faster speed because of the stock timing cl17 . Funny thing is all of my memory benchmarks read 1 less value than what I am running in the bios. Cl17 comes back as 16 for latency and 16 comes back as 15 in tests. I also have a XI Extreme. I really like that board also. So far, the Extreme scores better in benchmarks. Memory is lower and the 970 Pro ssd is much lower. Graphics looks to be higher, but I can not be sure until my other cpu gets back to me. (IHS came off). Some of the above I believe is user error.
 

I do not believe G.Skill has any ram listed for this board posted, yet. I have not asked G.Skill support. I was just using what I have. The only other RAM that I have is Corsair 4000cl19 and Dominator 3000cl15.
 
 
OOh, I see what you did there.
 

Ok, thank you.

I emailed g.skill describing my problems, and an answer came in 15 minutes. 
 
"BIOS is not ready, use a motherboard on the G.Skill QVL if you would like to achieve the rated specifications:
 
https://gskill.com/en/product/f4-4600c18d-16gtrs
 
Thank you
GSKILL SUPPORT"

Thanks for linking to that thread! LOT of good info by Kingpin in there.

You might be putting too much voltage through the IMC. 1.5v? Dude. We don’t even go that high on LN2. You could have done some serious damage with that.

As said above, it might be your IMC. Running extreme clocks takes a lot of tuning. It’s not easy. Your best bet is to start low and avoid the 4000 strap as it’s apparently causing issues. Try to skip it and go to 4133 or 4266 and see what happens.

Vince’s profiles aren’t guaranteed to work with everyone else’s modules. It’s a starting point provided your hardware is capable.

I did it with mine just took around 1.4v vccsa and vccio

Rog realbench stable 16gb density 1hr

i sent them back, but Im saying thats what it took.  personally I was gonna use them for low lat OC, but i didn;t have a great cpu to test and the OC guide wasnt up when I still had the sticks.. 

You leave subtimings on auto? And if it’s not too hard for you can you post the screenshots of subtimings, so that I can try to put them in manually?

Are you able to run them faster than 4000 with or without tighter timings?

I can run 4300 at stock timing using the same G.Skill 4000 17-17-17, but can not run lower timing. Go figure...huh? I tried your setting at 43, 42, 41, and then 40 with no luck. Good for you, for sure.

Sajin
Possibly. See if adjusting your vccio & vsa voltages to 1.35 volts will help get the memory running.

Do you think 1.35v vccia and vsa is safe for 24/7?