Really need help....Please someone - Overclocking 920D0

Hi all,

Spent the last 2 weeks now messing about trying to overclock my 920 D0. I have an Asus Rampage 2 Extreme motherboard, Corsair Dominator 1600 6GB (3x2). The cpu is water cooled with a heatkiller and I have a 4870x2 also in the loop.

It's really getting me down now because all I seem to be doing each night is testing, testing and more testing.

I managed to get 4ghz stable in Linx and Prime 95 using:

Vcore - 1.275
Vtt - 1.275
Vdimm - 1.65

All other voltages are set to manual, lowest.

I have LLC enabled for this clock. When I check the idle voltage load in cpu-z it says 1.264 and under load it stays the same in cpu-z but in everest is goes upto 1.32-33 (load).

I thought LLC kept the voltages more or less the same, regardless of load, when it was enabled?

Is CPU-Z correct as in the voltage stays the same under load too or should I take what everest is saying as true?

I then read it's better for the cpu and motherboard to disable LLC as it gives a much cleaner power and voltages will drop on load.

I tried to get 4.2 stable with LLC off, I set the vcore to 1.375 and in cpuz it showed 1.36 and under load it went down to 1.256 which is a massive drop and the inevitable bsod occured. I then set vcore to 1.4 and again it dropped massively under load.

I'd really appreciate it if someone could explain LLC to me in simple terms and whether its better on or off?

Why is my load voltage dropping so much also, do I have a potential fault?

Really hope someone can help me, just about come to the end with it.

Many thanks,

RoEy

Good Day RoEy , i went thru 4 Asus Rampage II eXtremes Mobos , all of them were punished in subzero benching very hard for many many months since the first day this mobo came out i put it thru the paces. I have never seen that kind of behaviour on any of my past boards (4) , i believe you have a faulty mobo and you need to RMA it back to Asus , but first post your specifications and lets troubleshoot before you send it for RMA,Post the specs, all of them including PSU and OS and software.


Regards: Chispy.

Hi chipsy,

Full Spec:

920 D0
R2E
6GB Corsair Dominator 1600
Sapphire 4870x2
Corsair HX 1000
Custom Water
Windows 7 Pro 64
Not muchn software installed except for a few games, nero burning rom, winrar, steam, xfire. Not much at all.

Going to be gutted if it is faulty. I've had it for a year now also and it's always done it. I used to run a 920 C0 at 3.6 on it before and the voltages then went up from 1.32 to 1.35 during load.

Thanks for the help so far,

RoEy

Keep it on RoEY, at these voltage levels it won't harm anything. It's typical Rampage/Gene II behaviour that under load the Vcore rises above ya set value with LLC on ... don't worry about it... with the REX II measure it, software readouts are not always 100% spot on...

My board has 2 LLC settings. Level 1 and Level 2.
If I use level 2, my voltage increases under load just like you are seeing. As long as your heat looks good I don't see why this would be a problem for you, as 1.35v is nothing too crazy.
Just leave it on!

Quote:

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Originally Posted by Leeghoofd

software readouts are not always 100% spot on...

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^^ This +1, eventhought the voltages shown by software seems a little higher than usual on my past experiences with this board , i never saw a big jump in voltages like you under load with LLC enable using my DMM. Try using a DMM for read out correct voltages , i have never trusted software for that. Good Luck.

Ok guys, thanks for all the help.

It's always done it from day one yet worked perfectly fine. I'd really like 4.2 but I think I need around 1.33vcore in bios for that, with LLC enabled and under load it goes upto 1.38, so everest/lcd poster says anyway. Would this be ok or not?Cpuz and hwmonitor say it stays roughly the same. Think I'll get a mulitimeter to check correct voltages.

So it's highly unlikely the board is faulty then?

Think I'm going to update to the latest bios too.

Thanks again,

RoEy

Updated bios to 1802 and it may have slightly helped.

Just clocked to 4ghz, 1.325 for both vcore and vtt in bios. LLC Off / all power saving stuff off, spread spectrums disabled / speedstep disabled/ etc..

Cpuz read it as 1.296 idle and went down to 1.232 under load, so still a big drop but not as big as I was getting before.

As you can see in the image provided, cpu-z and hwmonitor read voltages the same but everest and asus probe read load voltages at 1.28.

I'd really like to run it with llc off if possible but can someone tell me if the drop looks any better, i,e, closer to normal?

Which 2 do I believe until I get multimeter? :confused:

http://i930.photobucket.com/albums/a...oey/llcoff.png


Thanks again people,


RoEY

Tried to get 4.2 with llc on and off.

With it off, I get bsod even with the vcore and vtt both set as high as 1.375.

(1.336 in cpuz idle)

Again, in cpuz the load goes down to 1.272 then I get bsod. Is it safe if I push vcore in bios to 1.4? Maybe that might be enough.

With llc on, Im using 1.33750 for both vcore and vtt, 1.328 idle in cpuz and it stays the same under load in cpuz and hwmonitor but in everest and probe it shows the vcore going upto 1.38-9 under load.

Are these safe voltages if it is going this high?

Will deffo get multimedter because I'm just not sure which to believe.

RoEy

Try to increase vPLL, vNB

LLC and Full Phase - Auto

both option may increase core voltage during Stress Load

Ill try what you said. I have got a DMM now and I haven't got a clue how to use it. What setting do I put it on?

Where do I plug the red and black wires into?

There's voltage points on the R2E so I just need to know what setting I put it on to test vcore?

Useless with electrics...:rolleyes:

http://i930.photobucket.com/albums/a...-33b_woblf.jpg

Thanks,

RoEy

Quote:

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Originally Posted by PatRaceTin

LLC and Full Phase - Auto

both option may increase core voltage during Stress Load

---

I have LLC enabled and Phase set to full phase.

RoEy

Ok, I managed to set it up right, I think, and I set it to 20 under V as I don't have 2 available. I thought about setting it to 1.5 but I'm not sure if this is right.

Believe or not, everest is the closest to volts. Cpuz is useless for me.

At 4.2, I have vcore and vtt both set to 1.33750 in bios.

When in windows I used the dmm and voltages were:

idle:

vcore - 1.33 (everest reading was 1.33 / 34)

vtt - 1.32 (everest reading was 1.33)


load linx:

vcore - 1.37 / 8 ocasionally (everest reading was 1.38)

vtt - 1.30 (everest reading was 1.31)


Is it safe to run these voltages with llc on or is there too much voltage spike, i.e., going from 1.33 idle to 1.37 load(dmm reading) ?

Thanks again,

I'll get to do some gaming one day this year. :D

RoEy

I have a R2E also and with LLC enabled, my vcore also rises under load when measuring with a DMM or using everest/Asus probe - everest is very close to the multimeter reading. I really hate this behaviour and wish Asus would just make it stay the same or better yet, droop say 0.02v under load with LLC enabled.

To use that multimeter above to measure vcore voltage, you see how the dial is pointing to 200m? Clockwise from 200m (means up to 200 millivolts) is 2000m (means up to 2000 millivolts) then '20' (means up to 20 volts) - set it to 20 ie from 'off' position, turn it 3 clicks clockwise.

EDIT - See the V symbol with the solid line and dashes below it? This means voltage DC section (basically from 12 to 3 o'clock on the dial). The 1.5 is in the Voltage AC section (3 o'clock to 6 o'clock) which is not what you are measuring.

Morning cryptik,

Done yet some more testing.

This time I test 4ghz with LLC off. DMM Readings:

Bios:

Vcore - 1.325

Vtt - 1.325

In windows:

1.30 idle

1.27 load

This seems a much better drop doesnt it?

Cpuz says it goes from 1.30 down to 1.23, which is completely wrong.

Deffo using everest from now on.

Does this seem ok?

RoEy

P.S. I did set it to 20 by the way.

yep that's very fine, you just saved yourself some cash :) enjoy the board mate...

Quote:

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Originally Posted by Leeghoofd

yep that's very fine, you just saved yourself some cash :) enjoy the board mate...

---

Thank god for that! :clap:

Now last question,

I want llc off permantly:

For example I think I'm close to getting 4.1 stable dmm readings:

1.3375 vcore and 1.325 vtt in bios

1.31 in windows idle and 1.28 load.

Think I may need to push it a bit more to get me to 4.2

Whats a safe idle vcore/vtt for 24/7?

Thank you all for your help, I feel much better now and can see some gaming sessions coming soon. :)

RoEy

try upping cpu pll to just under 1.9v(i use 1.86v@4.2ghz and 1.9v@4.4ghz)
and def raise vcore, around 1.45 is safe for WC setups(i use 1.40v@4.2ghz and 4.4ghz)the trick after 4.2ghz is the QPI VTT(not QPI PLL)likes to be around 1.5v-1.6v(i always stay under 1.6v)

my setup is:
i7 920 DO WC Koolance 350ac
x58a-ud7 WC standard
dominator GT 1866mhz DDR3 6GB(soon to be WC with RAM-33 from koolance)
GTX 295 WC Koolance NX295s
2 x 1tb f3's in raid0
1 x 1tb f3 storage
toughpower QFAN 750w
xspc 360 rad,mcp655-b,custom 20ltr external res

Quote:

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Originally Posted by pooal

try upping cpu pll to just under 1.9v(i use 1.86v@4.2ghz and 1.9v@4.4ghz)
and def raise vcore, around 1.45 is safe for WC setups(i use 1.40v@4.2ghz and 4.4ghz)the trick after 4.2ghz is the QPI VTT(not QPI PLL)likes to be around 1.5v-1.6v(i always stay under 1.6v)

my setup is:
i7 920 DO WC Koolance 350ac
x58a-ud7 WC standard
dominator GT 1866mhz DDR3 6GB(soon to be WC with RAM-33 from koolance)
GTX 295 WC Koolance NX295s
2 x 1tb f3's in raid0
1 x 1tb f3 storage
toughpower QFAN 750w
xspc 360 rad,mcp655-b,custom 20ltr external res

---

Ok thanks for this.

I take it you have llc off?

RoEy

Quote:

---

Originally Posted by pooal

try upping cpu pll to just under 1.9v(i use 1.86v@4.2ghz and 1.9v@4.4ghz)
and def raise vcore, around 1.45 is safe for WC setups(i use 1.40v@4.2ghz and 4.4ghz)the trick after 4.2ghz is the QPI VTT(not QPI PLL)likes to be around 1.5v-1.6v(i always stay under 1.6v)

my setup is:
i7 920 DO WC Koolance 350ac
x58a-ud7 WC standard
dominator GT 1866mhz DDR3 6GB(soon to be WC with RAM-33 from koolance)
GTX 295 WC Koolance NX295s
2 x 1tb f3's in raid0
1 x 1tb f3 storage
toughpower QFAN 750w
xspc 360 rad,mcp655-b,custom 20ltr external res

---

This is not true for all setups. I use 1.290v Vtt for 4.5GHz Linx max mem stable. I would not recommend using over 1.40v Vtt 24/7 but that's my opinion.

Quote:

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Originally Posted by CryptiK

This is not true for all setups. I use 1.290v Vtt for 4.5GHz Linx max mem stable. I would not recommend using over 1.40v Vtt 24/7 but that's my opinion.

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That's impressive vtt cryptik, lucky sod. :D

I'll try and get 4.1 stable, 21 x 196 then I'll go for 4.2 and leave it at that. Just so pleased I got the DMM out. CPU-Z = Poo:p:

RoEy

Quote:

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Originally Posted by CryptiK

I use 1.290v Vtt for 4.5GHz Linx max mem stable. I would not recommend using over 1.40v Vtt 24/7 but that's my opinion.

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+1 me neither,nice vtt by the way.I've seen alot of rumours that cpu vcore and vtt should be near equal, but that is not exactly correct i'm sure!! but under 1.4v vtt on my setup and windows takes longer too load, wich to me is signs of instability so i stay between 1.4-1.5 vtt.

Roey- without llc at 4.4ghz i get bsod randomly with vantage when it's running cpu test, i have not tryed without it on prime or linx..YET..cause if it fails vantage then i don't bother with the others.

Here's my current BIOS profile for the rig in sig. Please use as a refsed in Everest. ference point to start and or comment on any use ov voltages. For my i7 920 version I was able to git 4.10GHz 205x20, DDR1649) but needed 1.34 vcore, 1.88 PLL & 1.32 QPI as used in Everest. (in BIOS; CPU=1.35, PLL=1.86, QPI=1.35) The i7 920 (DO) had the potential for 4.2 w/ added vcore PLL. I think I used BIOS vcore 1.4, PLL 1.90

Also not in this Prime stable profile I got full use of ACPI S3/S4 modes (sleep/hibernate) once again by leaving ACPI 2.0 support to OFF, Suspend mode to AUTO, post video on Resume from S3 NO

ASUS RAMPAGE II EXTREME PROFILE BIOS 18xx
Intel i7 930 batch #3951A824
BIOS Setting Everest
CPU Frequency 4200
DRAM Frequency 1600
Extreme Tweaker
BCLK Frequency 200
CPU Multiplier 21
PCI-E Frequency 210
DRAM Frequency 8
UCLK Frequency 3200
QPI Frequency 7218
DRAM Timing Configuration
1st Timings [6-8-6-24-5-88-14-8-24-4]
2nd & 3rd Timings AUTO
EPU II Phase Control FULL RANGE
Load-Line Calibration ENABLED
CPU Differential Amplitude 800
Intel Turbo Mode DISABLED
Voltages set Everest
Vcore 1.33250 1.323
PLL 1.86892 1.865
QPI 1.33650 1.320
IOH core 1.20616 1.204
IOH PCI-E 1.5v 1.52431 1.521
ICH core 1.20616 1.204
ICH 1.5v 1.52431 1.515
DRAM Bus 1.65681 1.654
DRAM Ref AUTO
CPU Configuration
CPU Ratio AUTO
C1E Support ENABLED
Adjacent Cache Line Prefetcher ENABLED
Intel VTT ENABLED
CPU TM 2 ENABLED
Execute Bit Disable ENABLED
Intel HTT ENABLED
Active Processor Cores ALL
A20M DISABLED
EIST (Speed Step) DISABLED
Intel Turbo mode optional if using EIST DISABLED
C State Mode ENABLED
Other Settings
Debug Mode STRING
Keyboard TweakIt Control DISABLED
CPU & PCIE Speed Spectrum DISABLED
CPU & PCIE Clock Skew AUTO

I'm having difficulities getting 4.1 stable. I'm now at 1.375 vcore and 1.35 vtt in bios. It either gives me a bsod or says it stopped due to error during Linx. This is with llc off.

I get a lot of the 124 bsod so I raise the vtt and it crashes even quicker so I lowered it back down. All other voltages are auto so I'll try messing with them but it feel like I've been trying to overclock forever.

Really need to sort it this week once and for all. I might just stick at 4ghz as I can get that stable with 1.3 for both vcore and vtt llc off. I think I'm going to need a massive bump in voltages to get 4.2 stable, which isnt worth it in my opinion.

RoEy

"DRAM Timing Configuration
1st Timings [6-8-6-24-5-88-14-8-24-4]
2nd & 3rd Timings AUTO "

i hope by auto you mean "quick tune" or that your setting all three channels to the same latency by just setting the one reference for all!!

"UCLK Frequency 3200"
you need to up this just one more tad, don't have it even 2 x the dram have it say 2.2 x the dram and must not ever go below 2 x dram or serious instability may/will occur, i run mine near 3.7ghz when ram@1600, although i should prob check the benifits if any of raising the uncore from 2x to 2.2x the dram.

I need 1.396v with both LLC on or off for no BSODs at 4.2 Ghz with HT on. Bios volts need to be set to 1.475v (LLC off), or 1.425v (LLC on) to achieve this.

4.0 Ghz is fine at 1.344v.

Quote:

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Originally Posted by pooal

"DRAM Timing Configuration
1st Timings [6-8-6-24-5-88-14-8-24-4]
2nd & 3rd Timings AUTO "

i hope by auto you mean "quick tune" or that your setting all three channels to the same latency by just setting the one reference for all!!

"UCLK Frequency 3200"
you need to up this just one more tad, don't have it even 2 x the dram have it say 2.2 x the dram and must not ever go below 2 x dram or serious instability may/will occur, i run mine near 3.7ghz when ram@1600, although i should prob check the benifits if any of raising the uncore from 2x to 2.2x the dram.

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Yeah auto I mean as in, ioh/ich etc..

I've set ram timing, 8 8 8 24 and 1N

Set ram, uclk and qpi manually. I've always kept ulck double the ram freqeuncy so I may try nudging that up another.

Thanks,

RoEy

Quote:

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Originally Posted by bhavv

I need 1.396v with both LLC on or off for no BSODs at 4.2 Ghz with HT on. Bios volts need to be set to 1.475v (LLC off), or 1.425v (LLC on) to achieve this.

4.0 Ghz is fine at 1.344v.

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Is the big increase in voltages worth going from 4 to 4.2? I doubt there is much difference in terms of speed but then again I may be wrong.

I'm thinking 4ghz maybe better for me as I can get it stable around 1.3 llc off, plus the temps are lower but then again I did want ram at full speed, 1600.

Decisions decisions....

RoEy

You need major cooling for 4.2 Ghz with HT on. I managed to get mine down to <80 degrees with 100% load, but after much reseating and reapplying thermal paste several times, ad also with lots of fans.

To be honest, I dont think it is worth it over 4.0 Ghz, I just did it because I were bored.

Have you turned virtual technology off, i've heard of people getting an extra 300-400mhz out of there 920 DO chips by turning it off as it's only needed with vmware and virtual machines etc...and don't quote me on this next bit but i think it handles the compatibility options in win7 i.e.win xp mode or vista mode is run virtually.In my profile 1(4.4ghz) it is on and it don't effect me as far as i know, but all hardware no matter how alike, they always have different needs(voltages,clocks etc.) so it might benefit you!!

also if your only gaming i have tests here that show next to know dif in fps by switching HT off, as i see your into max stressing for verification of a stable overclock, the HT will be heavily used with the testing but yet not the practical realworld stuff you actually do so i.e. turn it off and check your gaming benchmarks, if they don't differ then leave it off and start lifting your clocks again, and vantage will differ i can tell you now by about p1000,
but crysis,farcry2 and dirt2 won't budge at all!!!

so do you want stable high clocks for gaming or are you after max stable clocks for heavy multithreaded enviroment i.e. prime,linx,media encoding,everest stressing

they are two dif ball parks trust me, i will now upload my results from my testing HT on and off in various games(crysis,farcry2,dirt2) and benchies(vantage,mark06,cinebench r10 and 11.5 and y-cruncher)i assure you turning it off will def help with your higher clock adventure, and not affect your fps in current DX9 or DX10 games, although you should know i have a review here of DX11 and it scales across cores very well, infact direct compute can have two threads all to itself, so next gen games will def benefit from multithreading in my opinion, so i'll post a pic of that as well... bck in halfa with all results

Quote:

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Originally Posted by RoEy

Is the big increase in voltages worth going from 4 to 4.2? I doubt there is much difference in terms of speed but then again I may be wrong.
RoEy

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mmm.LOL. yeah theres a noticible dif i will show you shortly, first the other results then i'll compare with 4.01ghz to 4.2ghz to 4.4ghz after my pluto pup 'n' chips..

Quote:

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Originally Posted by bhavv

You need major cooling for 4.2 Ghz with HT on. I managed to get mine down to <80 degrees with 100% load, but after much reseating and reapplying thermal paste several times, ad also with lots of fans.

To be honest, I dont think it is worth it over 4.0 Ghz, I just did it because I were bored.

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he is watercooled, not aircooled.. and gaming does not need the extra cooling only the heavily multithreaded stuff does, i have an atomic magazine review here that even states that gaming rigs only require a portion of what mediaencoder rigs require in cooling i.e. i7 920@4.2ghz on a gaming rig would be lucky to see 65c after hours of play(roey i hope you have a descent rad)where a media encoding rig at same settings would be lucky to stay under 75c

hence what i previously said "is it for heavily multithreaded apps or just gaming" the two rigs in my opinion should be tuned differently(in regards to temperature concerns that is). to back this statement i will post temps @4.4ghz between crysis,farcry2 and prime,cinebench r10 'n' 11.5....

Morning Pooal,

Thanks for all the info so far and I'm looking forward to the results you're going to post.

To be honest, I'll mainly be gaming on it and I don't do any encoding. I was doing more testing lastnight and it looks like I'll need over 1.4 vcore LLC off to get it stable at 4.2. I don't really want to have to use that much voltage so I think I'm going to settle for 4ghz. Need to sort it this week once and for all. I'll try the virtual tech tonight though, thanks.

Radiator is TFC QUAD so I have the cooling power.

Many thanks again,

RoEy

Waiting for the results......:D

RoEy

For me, 4.2 - 4.3 GHz is my sweetspot. I notice games are smoother compared to 4 GHz (especially Crysis) and obviously other CPU intensive tasks benefit from the higher clocks. I run HT on for the added power in multi threaded apps/encoding/rendering. It really just depends on what you use it for, and whether or not the gains of higher clocks are perceivable / worthwhile. I run a TFC Quad too, and temps are manageable at up to 4.5 GHz (and my CPU is very hot) so you should have the headroom.

I really want 4.2 but I'm just worried about going over 1.4 vcore with llc off. Plus I think I'll need high vtt too.

I havent altered cpu pll, ich voltages etc.. so they may help stability.

RoEy

You just need to choose a voltage for vcore & Vtt you are comfortable with, and go as high as that allows. No point feeling uncomfortable to get 4.2 GHz.

Quote:

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Originally Posted by CryptiK

You just need to choose a voltage for vcore & Vtt you are comfortable with, and go as high as that allows. No point feeling uncomfortable to get 4.2 GHz.

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Yeah I agree with you.

RoEy

:clap:..finally, heres the ht off and on comparison, sorry about the delay been off doin stuff,the list goes off, on, off, on..... i'll get some 4.01,4.2,4.4ghz game and multithreaded temps up shortly(prime, everest stress and ychruncher vs crysis,farcry2 and dirt2) including my volts and settings..:up:

Quote:

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Originally Posted by RoEy

I really want 4.2 but I'm just worried about going over 1.4 vcore with llc off. Plus I think I'll need high vtt too.

I havent altered cpu pll, ich voltages etc.. so they may help stability.

RoEy

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The 1st thing you will need to increase is the PLL. For a 4.2 and above stable without having to crank up the vcore you will likely need to start around 1.86 to 1.88 but it is not unusual for a 4.2+ to need or want 1.90v PLL. This is a quad and they really do benifit from raised PLL to stable out. 2nd, follow the profile I posted earlier on page 1 as a guide. Use manual voltages where as much as you can, even if set to default.

You can maybe get away with UCLK, QPI, & CPU Differential frequencies to AUTO but you should set the rest I pointed out manually. I also sugest upping the PCI-E bus if to stable out USB stuff especially or onboard sound and USB mouse for starters. Try at least 110 but some need or like 115. Notce the increase in NB/SB cores, they like at least 1.20v and it is not unusual to need 1.30v on NB & 1.35 on SB. I would play with NB/SB PCI-E 1.5v and test with 1.52v for now, lower if stable later. In CPU config, DISABLE everything but HTT for now till you get stable. I honestly dont feel you should need more then 1.35v (in BIOS) for QPI, but some do need or want 1.4 but that has more to do with RAM and timings I think. (somebody can confirm for us).

Last, but should be 1st, set RAM to a 2:4 ratio if able to hit 1600 with auto timings for now just to leave out of OC testing. Once you get CPU to where you like, go back and dial in timings and continue testing as it may change due to QPI, UCLK and timings, but at least you will know. Also, make sure no GPU overclocking is going onduring any of this yet.

Try this and let us know how it goes.

Did you up the ioh core as well?

Quote:

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Originally Posted by Nuckin_Futs

The 1st thing you will need to increase is the PLL. For a 4.2 and above stable without having to crank up the vcore you will likely need to start around 1.86 to 1.88 but it is not unusual for a 4.2+ to need or want 1.90v PLL. This is a quad and they really do benifit from raised PLL to stable out. 2nd, follow the profile I posted earlier on page 1 as a guide. Use manual voltages where as much as you can, even if set to default.

I also sugest upping the PCI-E bus if to stable out USB stuff especially or onboard sound and USB mouse for starters. Try at least 110 but some need or like 115. Notce the increase in NB/SB cores, they like at least 1.20v and it is not unusual to need 1.30v on NB & 1.35 on SB. I would play with NB/SB PCI-E 1.5v and test with 1.52v for now, lower if stable later. In CPU config, DISABLE everything but HTT for now till you get stable. I honestly dont feel you should need more then 1.35v (in BIOS) for QPI, but some do need or want 1.4 but that has more to do with RAM and timings I think. (somebody can confirm for us).

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I don't think he mentioned any troubles with usb or pci-e and i have never ever had to stabilise an overclock with the pci-e settings in bios so i'm not sure what you mean there, if anything the recomendation is to not go over 105mhz incase you cause GFX card damage and or corrupt data.Besides why would you overclock your pci-e it changes almost nothing and almost certainly nothing over 105mhz and i have tested it on numerous GFX cards.
I'd agree that the extra ram speeds etc. would cause extra stress on the QPI seems logical!! but i have never had to increase QPI VTT going from cas7-1333mhz to cas7-1866mhz manually but if done via the XMP setting then it automatically sets QPI VTT to 1.6v up from 1.175v wich is extremely dangerous for the chips lifespan, and when the voltage is lowered bck to 1.175v no stability issues occur so i am sure this is not an issue for most.

XMP Profile1https://v3.server-builder.com/Wizard...ample_jpeg.jpg

XMP disabled https://v3.server-builder.com/Wizard...2fexample2.PNG