6900k IMC Troubles

R

Ryme

New member
Hello all,

First post here hoping to get some help with my new baby. I'm an old school gamer but new to X99. I recently graduated from a 2600k @4.5ghz when I came into the opportunity to build my dream rig.

Problem - My 6900k can overclock and be stable at 4.0ghz with my Corsair Dominator 3333mhz memory set to 1333mhz. If I try to bump it up to 3200mhz the machine will boot and pass Prime95 (with avx) no problem, but all games crash within a few minutes leaving me back at the desktop. WTH?

So I've done some research and I have found that the IMC (internal memory controller?) on the 6900k isn't exactly fond of super speedy memory.

Problem - What I don't know is how to fix this. I would assume that we can give "something" a bump which would give the o'l girl the ability to run the ram at least close to it's rated speed. I would be happy with 3200mhz, but would really prefer to run her at 3333mhz which is what I paid for.

Thoughts, Ideas, insane ramblings?

Rig
Asus Rampage V Edition 10 (siiiicccckkkkk!)
PC Power & Cooling T12w 1,200w single 100A 12v rail
6900k at stock while figuring this out :-(
H115i
Corsair Dominator 3333mhz DDR4 8x4 32gb
Samsung 950 pro m.2 (512gb)
GTX1080 SLI - Asus Strix
Raid 0 intel 730's 480GB (lame onboard controller)
Corsair 750D Air Flow (with noctua Industrial 140/120mm fans every-friggin-where)

Over kill? Yes...but it'll last me just as long as that 2600k did. I am also a fellow YouTuber who goes by the name ColoradoDualSport

Thank you TTL for all of you videos. They really helped me out!
 
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Dang! Of course I missed one thing. Yes, BIOS is 1003 (I think that's correct) released on the 13th of this month.
 
1st off, welcome to the forums!

Right, to start with, remember the 6900K only officially supports up to 2400mhz. Everything past that is an OC and is not guaranteed to work at the speed that the memory is rated to support.

The 6900k IMC is a mixed luck bag when it comes to getting support for 3000mhz+ memory to work. Once again, silicon lottery has a huge part to play, some chips have weaker IMC's than others. They will also vary dependant on your OC on the cores.

There are two main voltages you can bump to give the IMC a boost. IO (VCCIO) and System Agent (VCCSA). Be aware when changing the voltages on these, the IMC will respond as badly to too much of a bump as it will to not having enough voltage. I would personally aim to get 3000mhz stable and see where you stand. As with core clocking, you are better off playing the long and fun game of small increase on speed, get that stable, then a little more speed, then get that stable ..... and so on.

On the flip side, you will see very little increase in performance with memory speed compared to any other overclocks that you do.
 
Thank you sir! That is exactly the information I was looking for! Going to have another go right now. I hope to hit 4.2ghz, but since I know 4.0 is stable with my settings so far I will start from there with the memory. Wish me luck.
 
Ok, I have confirmed that I am now stable at 4.0ghz 1.2v Vcore 34/34 cache ratio and 1.8v on the cache.

Ram is now set to 2400mhz

Temps are awesome at 42c after a full game of battlefield 4! As I mentioned before I know that these settings are stable after a few hours of Prime95/avx.

Ok, next question. Since we now know that it really is the IMC giving me fits. What would you suggest trying to get 3200mhz stable? I should have looked at the auto voltages but I forgot. It's been a long day.
 
32gb is pushing it for fast memory speeds.

If you don't need all that capacity 16gb would be a lot easier to run @3200mhz+
 
Kaapstad said:
32gb is pushing it for fast memory speeds.

If you don't need all that capacity 16gb would be a lot easier to run @3200mhz+
Click to expand...

Not really intention of stealing the thread, but if I may just ask Kaapstad, what about 64GB at 2800MHz then?...
 
Chrazey said:
Not really intention of stealing the thread, but if I may just ask Kaapstad, what about 64GB at 2800MHz then?...
Click to expand...

I have never tried it but I suspect it is quite possible.

All my PCs use 16gb as it is best for gaming and benching.

One of my 6950Xs runs with some 3400mhz memory that can overclock quite a bit past that.

I am not a great fan of DDR4 as it seems to offer not very much when you increase the speed or reduce the timings.
 
Kaapstad said:
I have never tried it but I suspect it is quite possible.

All my PCs use 16gb as it is best for gaming and benching.

One of my 6950Xs runs with some 3400mhz memory that can overclock quite a bit past that.

I am not a great fan of DDR4 as it seems to offer not very much when you increase the speed or reduce the timings.
Click to expand...

How so?...
 
tinytomlogan said:
1.8v on the cache? I hope not.....
Click to expand...

You are correct, I miss spoke. 1.5v (<- incorrect 1.15v)which was suggested in this video here. Which was actually lower then what auto had it set to. (go figure) His settings were spot on for stability at 4.0ghz https://youtu.be/dW6gBneg3VA?t=233

So I don't misspeak again I took pictures of the current settings. What do you guys suggest for VCCIO (one or both?) and VCCSA for targeting 3200mhz? Also, I know that auto is never the way to go, so do you guys spot anything else that should be manually set for safety?

I am running 32GB as it helps a lot with video editing. This weeks video on my channel in case any of you are interested in dirt bikes as well as computers. I may be the only one that is. If this link is a problem feel free to remove it admins. https://www.youtube.com/watch?v=wH7580b9eF8

New question - Hypothetically - If we are able to get this kit running at 3333mhz, is there any reason to switch from using the multi to using the 125mhz CPU strap to overclock to 4ghz? I noticed that when I enable XMP it automagically sets the cpu strap to 125 and therefore overclocks the cpu to 4.0ghz. I did the math....yes I'm a bit of an idiot some times. 125x32=4000 ish. Is there any real benefit to using the milti instead or is it just the way everyone does it....for no real reason?

Again, please excuse my noobish questions. The last time I was heavily involved in manual over clocking was with FSB and a Q6600 (which was a beast I loved)

s%21An4LD5tqmQA2ihzrDy7Dpj27KmdY

s%21An4LD5tqmQA2ihuv2XDJS0BSpcLy

s%21An4LD5tqmQA2ih3guMBmajrt0RqH

s%21An4LD5tqmQA2ih3guMBmajrt0RqH


My end goal is 4.2ghz stable for 24/7 usage. From what I have read anything over 4.2-3 requires a ton of voltage and I'm more intrested in longevity then benchmarks. This rig already screams and Fire Strike Ultra says it's better then 97% of machines tested. http://www.3dmark.com/fs/10249201
 
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When you guys are right, you're right.

A small bump in VCCIO and VCCSA did the trick. 3200mhz running stable. CPU is now at 4.4Ghz at 1.275v Temps in a brief Prime95 run were 83c max.

Going to let her burn in over night and see if she's fully stable.

Thanks again.

Just to finish this off for anyone searching later on with the same issue. Prime95 ran all night last night without fail max temp was 85c on the mixed test.

I am a happy camper and even got 200mhz over my goal. I will post BIOS screen shots when I get home tonight.
 
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