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Running and Overclocking 8x DDR4 Modules

Level 10
In this thread I want to do two things:

1.) Share which adjustments were necessary to get 8 DDR4 modules of a total memory amount of 64 GB running @2400GHz, which was not out-of the box in my case. The adjustments I needed may help others as a starting point.
2.) Ask for advice which screws I might try for a higher memory clock.

First of all, I am running a 5820K@4.4GHz in adaptive mode at 1.32 V turbo voltage, rock stable, BIOS V.1701. I purchased new RAM: HyperX FURY DDR4-2666 15-17-17-35, 1.2V (double-sided with Hynix chips). As 64 GB Kits seemed either overpriced or have currently limited availibilty, I decided to do some gambling and ordered two kits of 4 modules each, at reasonable costs of total 410 Euro (what you are not advised to do at all unless you are a little masochistic!-The-meat-and-potatoes-o...).

1.) After installing all eight modules, I was not surprised that XMP 2666MHz was not stable. But I was surprised that also 2133 MHz on “auto” was not stable, even not at timing cycles of the 2666MHz profile (this is for example 15-17-17-35).
But I did achieve stability at 2400 MHz for the following intervals of voltage adjustments (I havent tested for 2133 MHz):

DRAM Voltage 1.285-1.325 V
VTTDDR Voltage 0.67-0.7 V
VPP DDR Voltage 2.62-2.87V
DRAM frequency 2400 MHz (where DRAM timings can be tightened a little).

Amazingly for all three voltages only certain intervals are possible, exceeding them has adverse effects!
Note that some characteristics I found may be rather determined by the CPU’s memory controller (IMC) than the memory itself.

2.) I understand for highest overclocks only 4 modules are advised but I wanted to see all the slots populated 😛
Now, I am flirting with getting maximum speed out of the RAM and maybe even reaching 2666 MHz. I tried many adjustments at 2600 MHz but without achieving stability: SuperPI for memory stability testing gives rounding errors (best after 10 minutes).
What can one specifically advise for overclocking 8 modules? Which screws may I try now?
It is great the Rampage V offers so many memory adjustment options unfortunately little information about them can be found, as to DDR4 overclocking.
So what is worth trying with these settings:

PLL Termination Voltage (I have left untouched)
CPU Input Voltage (I tried raising by 0.05-0.15 V with no success)
CPU System Agent (Auto will set it on 0.96V and that seems a good guess - manually I found stability at 2400 MHz between 0.92V and 1.08V)
DRAM Swizzling (setting bit 0 and 2 to disables makes my system awfully unstable)
DQ Sense?
DQS Sense?
CMD Sense?
CTL Sense?
DRAM CLk Period?
BIOS the DRAM Timing Control/IO Control menu ??
DRAM Switching frequency?

Level 13

Neither PLL Termination Voltage or CPU Input Voltage has an effect on memory stability. Normally PLL Termination Voltage can be left on auto. CPU Input Voltage can be increased for CPU stability depending on the set VCORE and LLC used. For memory clocking CPU System Agent and memory voltages as well as the 4 primary memory timings should be concentrated on. The additional settings you list are beyond both the patience of most users as well as being too in-depth for explanation in a forum setting.

Level 8

I am using 2 kits of 32GB (2133MHz@CAS15) for few months now. I have not tried the stressapp yet (I will definitely try as soon as I found the time to do it), but it is stable at 2400MHz@CAS12 in realbench, aida, occt, games, daily tasks...
Here is how I found my settings (this is my own experience and do not take this as golden rules):
1. Put Vram at 1.35V (can be decreased later if stable or start higher/lower if you wish).
2. Plug only 1 kits.
3. Leave all ram timings to auto.
4. Change only the memory speed to find different CAS timing ( in my case 1600MHz@CAS11, 1666@CAS12, 1866@CAS13, 2000@CAS14, 2133@CAS15, 2400@CAS17) and take notes from the bios of the Primary, Secondary and Third timings for each speed.
5. Then you can run the 2 kits at 2400Mhz (or lower if not stable) and start from the higher set of timings, if stable try the lower ones.
6. Then you can redo the step 5 and increase RAM speed if your kits/IMC allows it.
7. After you can try to tighter the individual timings.

Hope this help someone, or if anyone has a better way to do it please share.

Here is the notes of my set of timings find by the auto rules at different Ram speed:
MB: Asus Rampage V Extreme (WC loop1 rad 120x3) Bios 4101
CPU: Core i7-6950X (WC loop2 rad 120x9)
MEM: G.Skill Flare X 32GB (4x8GB) DDR4 3200MHz@CAS14/CR1
GPU: ZOTAC Trinity RTX 3090 Watercooled [double side] {PCIE_X16/X8_3 slot} (WC loop3 rad 120x9 + 140x9)
SSD: Corsair MP600 PRO XT 2To SSD M.2 NVMe w/ heatsink
HDD: 4 x 10TB Seagate IronWolf RAID 0 (WC loop1)
PSU: EVGA NEX 1500 1650W + Seasonic Fanless TX-700W
Main Screen: ASUS ROG Swift PG43UQ 4K 144Hz G-Sync/FreeSync HDR

Level 10
Thanks for sharing!
In my case a manual Voltage adaptation is necessary for running eight modules.
So I am curious if anyone else would share his (stable) voltage tuning?