G.Skill 3866 won't boot in 3866 (Asus Z270F)

[robaczek]

Hi all, new member here, but avid Asus user for over two decades 😉

So, I just upgraded a few components, specifically I have now ASUS LGA 1151 STRIX Z270F GAMING Intel Z270 with G.SKILL F4-3866C18D-16GTZKW Trident Z Series 16 GB (8 GB x 2) DDR4 3866 MHz CL18 Dual Channel Memory Kit and i7 7700K running at stock.

I can boot into 3733MHz stable when I set:
CPU VCCIO Voltage - 1.20V
CPU System Agent Voltage - 1.23V

But I cannot boot at all into 3866 even when both are set to 1.25V (didn't try any higher). I have XMP turned on, so timings and voltage is set as per manufacturer recommendations. I already exchanged one exact same set to another thinking that maybe it was the memory, but no, second set also won't boot. Machine turns on, but screen after few seconds goes black (no signal), never showing anything. Then all I can do is press the power button (even the Reset won't work) after which the computer boots with safe settings with 2100MHz asking to go to Bios and make amendments.. Pls help 🙂

[Chino]

You can continue to tweak both voltages. But things are looking like you might have reached the limit of your CPU's IMC.

[Nate152]

Yeah, you may want to try increasing the Dram voltage to 1.40v.

[robaczek]

Nate152 wrote:
Yeah, you may want to try increasing the Dram voltage to 1.40v.

Thank you for your replies! That sounds strange, I mean according to the XMP profile, it suppose to work at this speed at 1.35V? Also, according to PCMag "Intel Kaby Lake Core i7 7700K with Asus Prime Z270-A can support up to 64 GB of memory with speeds of up to 3866 MHZ (O.C+)". So my question remains 🙂 I will check with 1.4V anyway and see if that helped..

[Chino]

robaczek wrote:
Thank you for your replies! That sounds strange, I mean according to the XMP profile, it suppose to work at this speed at 1.35V? Also, according to PCMag "Intel Kaby Lake Core i7 7700K with Asus Prime Z270-A can support up to 64 GB of memory with speeds of up to 3866 MHZ (O.C+)". So my question remains 🙂 I will check with 1.4V anyway and see if that helped..

It depends on your CPU. I would expect you need a golden CPU to run 64GB of memory at 3866MHz.

As for the VCCIO & SA voltages, you still have some headroom left. Follow these guidelines.

DDR4 frequency range	Required CPU VCCIO Voltage range	Required CPU System Agent Voltage range
DDR4-2133 ~ DDR4-2800	1.05V ~ 1.15V	1.05V ~ 1.15V
DDR4-2800 ~ DDR4-3600	1.10V ~ 1.25V	1.10V ~ 1.30V
DDR4-3600 ~ DDR4-4266	1.15V ~ 1.30V	1.20V ~ 1.35V

[robaczek]

Thank you VERY MUCH! I shall start my experiments momentarily! 🙂

[robaczek]

Well, I'm happy to report I managed to boot into stable 3866MHz! I changed the Dram voltage to 1.4V, then CPU VCCIO Voltage and CPU System Agent Voltage both to 1.3V and tada! It works! Now, this was a quick hack, to see if it will boot but 30 min. of Prime95 seems to confirm it is both stable and error free. Now, I will take some time to start lowering those numbers and see how 'low' I can get, but the bottom line is - thank you for your replies and assistance! At least I don't have to worry if my memory or MOBO is faulty anymore! Thx!

[robaczek]

ok, I lowered the voltage to 1.35V as per specs and now am experimenting with the other two but my question is, if I ever wanted to OC my CPU (i7 7700K) can my memory remain on this speed or will it work with faster speed when I amend the bus speed? I ask, because by running the Auto Tweak it changes the bus speed to 103 and that automatically changes the memory speed, too..

[robaczek]

ok guys, how do you test if the settings are stable? I mean, I spent an hour playing Dishonored 2 with no problems at all, but then when I run Prime95 it returned an error after like 2 minutes... I presume it should work without any errors, so as long as there are errors I just should up the voltage, right?

[Jldowning]

I'm having a similar issue. How did you get back into the Bios? I can't boot or anything... Did you reset the Cmos?