Trouble running Vengeance LED 64GB at 3GHz on XMP and Asus Gene

[Cazimodo]

I recently bought an Asus Maximus VIII Gene, I7 6700K and Corsair Vengeance LED 64GB (4 x 16GB) DDR4 DRAM 3000MHz C15 (CMU64GX4M4C3000C15R)

Whenever I enable XMP so that the memory runs at 3GHz I get a bunch of errors on memtest86.
The individual DIMMs work fine in pairs, it only has issues when all 4 are in use.
I've tried upping the voltage slightly to 1.3596 and also moving away from 3000MHz to 3066 and 2933 keeping the rest of the settings as per XMP, but no luck.

The memory however runs fine with XMP off and defaulting to 2133 MHz.

Any suggestions of what else I should try?

Thanks!

[kalniel]

I believe the 6700K only supports RAM up to 2133mhz, beyond that you're at the mercy of overclocking the CPUs integrated memory controller, which when running four sets is under more pressure than simply running two. You might need to concentrate on upping the IMC voltage rather than the DIMMs.

[Cazimodo]

Thanks, that seems to line up with what I'm starting to understand from reading since posting. On a side note it looks like it is stable at 2900MHz in memtest86. Just discovered stressapptest as an alternative.

Ok so I'm translating 'upping IMC voltage' to a process of upping CPU VCCIO and CPU System Agent Voltage in increments.

[kalniel]

Thanks, that seems to line up with what I'm starting to understand from reading since posting. On a side note it looks like it is stable at 2900MHz in memtest86. Just discovered stressapptest as an alternative.

Ok so I'm translating 'upping IMC voltage' to a process of upping CPU VCCIO and CPU System Agent Voltage in increments.

If only I had as nice a CPU as a 6700k to look and help you out A very quick google suggests VCCIO might be the one you want but as I say I don't have any experience of skylake. (If you have an old Nehalam based system and need a hand, give me a shout )

[Cazimodo]

Thanks for pointing me in the right direction, I'm using my Machine Learning studies as an excuse for the overpowered system

I managed to reduce the number of issues by upping VCCIO to 1.25, VCCSA to 1.25 as well as the DRAM to 1.45V at 3GHz but still had 2 or 3 issues on the hammer test in memtest. Dropped the DRAM back to 1.35 as per your suggestion but started getting more errors and changed direction. I could probably get it stable by pushing VCCIO a bit more but my Corsair H90 cooler did not seem to keep up with higher VCCIO settings under load with the CPU reaching temps of 98C.

I need to actually do work with the machine so I eventually decided to run it on 2.8GHz, and auto voltages for now which seems pretty solid in all the tests I'm running: memtest86, stressapptest, occt and strangely enough the most reliable complainer of the lot DOOM 2016