Core i7/X58 Overclocking Thread

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Originally Posted by T_Flight

Yes, it has to do with the physics and what these new CPU's and the Mem Bus and COntroller can withstand. It's a differential voltage problem. If you start getting away from a .5v diff between the QPI/DRAM (Vtt) and the DRAM voltage it could cause damage. This was Explained by Dr. WHo ina post on here early on right around release time. He also said that like all OC'ing to do so at your own risk.

In this case, I'd say the less diff the better. Since we usually deal with around 1.65v on the DRAM, we need to keep around 1.3-1.4v on the QPI/DRAM. 1.35v on the QPI/DRAM is the Intel max spec if I'm remebering right. I have 1.3v set in mine right now and it's fine on the rig in my sig. Be careful with Vtt though, becasue there is a limit, and if you go too high damage to the IMC can result. I don't think we know where that line is yet, but some have been running slightly over spec voltages with succsess although it doesn;t mean they'll be able to do that for long periods of time. It's all about the risk you are willing to take.

I'm on the more conservative side, and I'm very careful what I say about voltage because voltage can cure some problems, but it also kills these parts if one goes to high. AFter a bunch of reading, I've developed a feel for it, but I'm very careful what I do.

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Many thanks for the eplanation and for giving your reference voltages. I'm on the conservative side as well but was hoping to achieve 4Ghz with my 920. Unfortunately I'm still waiting for some WC'ing components and wiring (8-pin extender). I hope to receive all these components this week, so I can assemble everything this weekend and start to play with the settings. I just wanted to make sure that I don't screw up my new components immediately by not complying to the 0,5v differential.

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Originally Posted by SteveRo

concur - all chips about the same (I have the 965).
Also - lower multi with higher bclock also gives lower temps.

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That's really interesting, I'll test this theory.

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Originally Posted by dejanh

No, actually my chip does the exact same thing. I just did a 20 pass run maybe 2h ago. Same clock, same voltage. I used memory at 1691, 7-8-7-20-1T timings, uncore at around 3800MHz give or take a few MHz.

LLC was on auto in my run. CPUZ reported voltage showed 1.288V (not completly correct, but then again, only a DMM is really correct).

If however I set 20x200MHz, I have to use roughly 1.3V.

It's funny that OC with higher BCLK actually works better than higher multipler. Completly opposite of what we should be seeing.

No wonder all the chips basically clock the same across the versions (920, 940, and 965 XE).

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My voltage fluxuated from 1.288 to 1.296 during the Linpack test.

I just started trying to Oc this chip. My next step is to increase the memory to over 1600 Mhz and try to stabalize that.

I turned off HT and tried to get 4.4 stable, and just couldn't. I think I need to adjust something else besides vcore since I ramped it all the way up to 1.53 v and still unstable.

I'm using a new board. Asus P6T Deluxe. I'm familiar with the Gigabyte board more. It seems you have more voltages to adjust compared to the Asus.

The 940 is more expensive than the 920 and reacts similarly, but I'm selling my 920. I can't hit 210 bclk with it unless I increase qpi/vtt past 1.75V which is crazy. It does work really well at 200 x 19 w/ HT on though.

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Originally Posted by SteveRo

concur - all chips about the same (I have the 965).
Also - lower multi with higher bclock also gives lower temps.

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I have seen many people say this but I'd like to know why this should make sense at all?

Higher bclk = higher IMC stress and more bandwidth to feed the cores at the higher core clocks. There's no reason I can think of for a lower multi with higher bclk to lower the required voltage other than some bizarre motherboard implementation thing. I'm still a noob though.

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Originally Posted by JWMc

I have seen many people say this but I'd like to know why this should make sense at all?

Higher bclk = higher IMC stress and more bandwidth to feed the cores at the higher core clocks. There's no reason I can think of for a lower multi with higher bclk to lower the required voltage other than some bizarre motherboard implementation thing. I'm still a noob though.

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Unless when you increase the multiplier, the volts needed to stabilize it, are considerably more.

Take the E8600. It required more volts to do 450 x 10 compared to 500 x 9. The higher multi required more volts, which imo we are still seeing with the i7 processors.

Well I wish I could get my system to post at 210 bclk so I could test a lower multi but 200 is the highest I've tried successfully.

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Originally Posted by JWMc

Well I wish I could get my system to post at 210 bclk so I could test a lower multi but 200 is the highest I've tried successfully.

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I had that problem with my old chip. What qpi/vtt are you using? with this one, I'm at 1.35v.

I need 1.275 VTT for 19x200+HT. I'm actually backed down to 21x180+HT right now though but still at 1.275 VTT because I didn't feel like figuring out if a lower value would work. I required 1.375 VTT for 20x200+HT in Prime blend and I think the bump to 1.395v helped with 21x200+HT.

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Originally Posted by JWMc

Well I wish I could get my system to post at 210 bclk so I could test a lower multi but 200 is the highest I've tried successfully.

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I tried 19x211 and it worked for me. I tried running 3dmark06 and Vantage quiet a few times - it worked. CPU : 1.35 in BIOS and QPI : 1.335

Ran Prime95, it failed after 20 mins or so.

Yea it seems we can get many variations of 'stable' including LinX without true memory stability at high multi-threaded loads. :(

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Originally Posted by JWMc

I need 1.275 VTT for 19x200+HT. I'm actually backed down to 21x180+HT right now though but still at 1.275 VTT because I didn't feel like figuring out if a lower value would work. I required 1.375 VTT for 20x200+HT in Prime blend and I think the bump to 1.395v helped with 21x200+HT.

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Your chip seems to react like my 3837B017 regarding QPI and Vcore voltages, also there is some kind of binding between QPI voltage and Vcore, maybe its temperature related. :confused:

If you want to try, I got mine stable at 211bclock @1.5VQPI and 213bclock @1.55VQPI.

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Originally Posted by NBF

Your chip seems to react like my 3837B017 regarding QPI and Vcore voltages, also there is some kind of binding between QPI voltage and Vcore, maybe its temperature related. :confused:

If you want to try, I got mine stable at 211bclock @1.5VQPI and 213bclock @1.55VQPI.

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Is not dangerous for your chip those voltages?

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Originally Posted by NBF

Your chip seems to react like my 3837B017 regarding QPI and Vcore voltages, also there is some kind of binding between QPI voltage and Vcore, maybe its temperature related. :confused:

If you want to try, I got mine stable at 211bclock @1.5VQPI and 213bclock @1.55VQPI.

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Thank you for this information! What I fear may be true: I have a weak or at least mediocre IMC. :(

I think I read earlier in the thread that G.Skill support replied to an e-mail regarding QPI/VTT voltage that it is ok to go high with it as long as there is sufficient cooling. I'm hoping the Intel max VTT spec of 1.35v is only specified because of the issue with DDR3 kits requiring too much voltage and causing the voltage differential issue with the QPI. That and maybe also the increased heat.

I have read several pages from this thread (approx. from page 65 up to here). But it is still not clear to me what Turbo mode exactly means? Should I disable turbo mode for OC'ing and how about HT?

I would like to know because by the end of this week I will have my i7 system and want to start to mess with the settings.

Turbo - Intel's oc'ing feature, bumps up the multiplier under load. Some peeps run with turbo on but most turn it off. HT - usefull but requires more voltage and produces more heat under load, so most peeps turn it off to achieve higher oc.
GL with your i7 setup!

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Originally Posted by Pisklink

I have read several pages from this thread (approx. from page 65 up to here). But it is still not clear to me what Turbo mode exactly means? Should I disable turbo mode for OC'ing and how about HT?

I would like to know because by the end of this week I will have my i7 system and want to start to mess with the settings.

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Turbo = 21 multi on a 920, 22 multi on a 940 and I guess 23 by default on a 965. I think the Asus motherboards might still have the issue where you can't get the turbo multi to activate past certain clock speeds though.

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Originally Posted by Pisklink

I have read several pages from this thread (approx. from page 65 up to here). But it is still not clear to me what Turbo mode exactly means? Should I disable turbo mode for OC'ing and how about HT?

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The little things vary greatly between different i7 setups. You're going to have to test for yourself. Some chips/boards like the 21 multiplier that Turbo offers, some don't. HT kills some chips at high clocks, while others just experience increased temperatures.

It goes on, and on, my friend. I think that's part of the fun, though. Unless, of course, you're a certain individual with an MSI board who's about to throw his i7 rig out the window. :p:

If using Gigabyte board and F4beta bios and later, just think of turbo as an extra multi. So for i920 if you want to use 20 multi (stock) turn turbo off. If you want to use 21 multi, set turbo on, and you now have a permanent 21 multi (though bios still says 20).

If you have a board that enables TDP limits...read intels white paper, but GB bios ignores TDP, current, and temp limits so below paper does not apply.
http://download.intel.com/design/pro...=tech_tb+paper

Edit: my god Im a slow typist...3 posted before me..lol

slow pokes :D

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Originally Posted by kpablo

Is not dangerous for your chip those voltages?

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Its beyond Intel recomended max value, there is some risk.

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Originally Posted by JWMc

Thank you for this information! What I fear may be true: I have a weak or at least mediocre IMC. :(

I think I read earlier in the thread that G.Skill support replied to an e-mail regarding QPI/VTT voltage that it is ok to go high with it as long as there is sufficient cooling. I'm hoping the Intel max VTT spec of 1.35v is only specified because of the issue with DDR3 kits requiring too much voltage and causing the voltage differential issue with the QPI. That and maybe also the increased heat.

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I wouldnt call it a weak IMC before trying high memory clocks (2000+), maybe its only voltage hungry :cool:

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Originally Posted by NBF

Its beyond Intel recomended max value, there is some risk.



I wouldnt call it a weak IMC before trying high memory clocks (2000+), maybe its only voltage hungry :cool:

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Well I'm defining weak by the fact that it seems to require more voltage than others (and than Intel's safe max! :() and from Anand's research showing huge variations in the required VTT for the same other settings on the same board with two chips from different lots. I wonder if Intel bins the chips largely based on IMC quality and 920 users are lucky to get good ones? Certainly the faster default QPI speed on the 965 is at least part of the binning.

Well, after all this talk of BCLK I decided to do an actual test on mine. Low and behold, maximum BCLK of 222MHz (set in BIOS, TurboV/CPU-Z reports it as 221 for some reason but whatever)...

Anyway, 20-pass LinX run completed without issues using 1.47500V QPI/DRAM (VTT). I'd say this is not bad?! :up: :down: See screenshot below.

My quest to get something stable out of my 3836B043 chip continues on....
Here is the latest. It will run 3.75ghz @ 1.23v stable all day long with HT off QPI/VTT set to 1.33v 21x178

I enable HT and if I stress all 8 cores heavily within 5mins it will get the BSOD of "an uncorrectable hardware error has occured"

Now, I AM runnin on a 500w P&PC cooling PSU...
I also am runnin on stock heatsink and temps hit 80C pretty easily with all 8 "cores" being stressed....

Im wondering if its either of the above 2 or if my chip just plain sucks at high speeds with HT enabled....

I just ordered a scythe Mugen 2 heatsink to see if heat is the issue =)

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Originally Posted by GenTarkin

My quest to get something stable out of my 3836B043 chip continues on....
Here is the latest. It will run 3.75ghz @ 1.23v stable all day long with HT off QPI/VTT set to 1.33v 21x178

I enable HT and if I stress all 8 cores heavily within 5mins it will get the BSOD of "an uncorrectable hardware error has occured"

Now, I AM runnin on a 500w P&PC cooling PSU...
I also am runnin on stock heatsink and temps hit 80C pretty easily with all 8 "cores" being stressed....

Im wondering if its either of the above 2 or if my chip just plain sucks at high speeds with HT enabled....

I just ordered a scythe Mugen 2 heatsink to see if heat is the issue =)

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You cannot really clocks past 3.6GHz using the stock heatsink. 99.9% certain temps are killing your OC.

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Originally Posted by dejanh

Well, after all this talk of BCLK I decided to do an actual test on mine. Low and behold, maximum BCLK of 222MHz (set in BIOS, TurboV/CPU-Z reports it as 221 for some reason but whatever)...

Anyway, 20-pass LinX run completed without issues using 1.47500V QPI/DRAM (VTT). I'd say this is not bad?! :up: :down: See screenshot below.

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What frequency is your RAM and Uncore running at?