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Thread: Core i7 Vdimm/VTT Graveyard :D

  1. #1
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    Talking Core i7 Vdimm/VTT Graveyard :D

    So, i7 launched and we are all sufficiently scared of using more than 1.65v vdimm alright. Looking at the real world performance boost from running high mem clocks over easily achievable clocks with 1.65v vdimm or even less, it seems high clocks and hence high vdimm isnt needed for gaming and 24/7 at all...
    but THIS IS SPA... XtremeSystems!
    I know there are quite some people out there pushing for more, a lot more

    Please share your results here and i will do my best to update the first post and summarize the experiences. Did you kill an i7 with high vdimm? What vtt and vcore did you use? for how long? Are you running high vdimm without any problems? how high? whats your vtt? whats your vcore?

    Thanks!

    1.90v vdimm / 1.20v vtt = dead after 1 day (Engineering Sample CPU rev B) - rev B?
    1.90v vdimm / 1.20v vtt = dead after 10 days (Retail 965 rev C) - most likely freak accident/bios/board bug
    2.25v vdimm / 1.45v vtt = dead after 1 day (Engineering Sample CPU rev C) - buggy board?
    1.88v vdimm / 1.50v vtt= dead after 1 week (Retail 965 rev C) - most likely freak accident/bios/board bug


    1.65v vdimm / 1.20v vtt = ok forever according to intel
    1.80v vdimm / 1.30v vtt = ok for 7 weeks
    1.95v vdimm / 1.40v vtt = ok for 5 weeks
    2.05v vdimm / 1.45v vtt = ok for 5 weeks
    2.05v vdimm / 1.36v vtt = ok for 6 weeks
    2.00v vdimm / 1.50v vtt = ok for 8 weeks (cold)
    2.00v vdimm / 1.60v vtt = ok for 2 weks
    2.00v vdimm / 1.65v vtt = ok for 8 weks
    2.25v vdimm / 1.70v vtt = ok for 4 weeks
    2.30v vdimm / 1.35v vtt = ok for 2 week (cold)
    1.75v vdimm / 1.75v vtt = ok for 1 day (cold)

    Conclusion:
    Its been 6 months since Intel launched i7 and there have been less than half a dozen reported dead cpus.
    Considering all the torturing those chips go through with ln2 cooling and vcores in excess of 1.7v, vdimm in excess of 2.2v and vtt in excess of 1.7v, this is very good news.

    1.6v vcore, 1.6v vtt and 2v vdimm
    These seem to be 100% safe, as long as the processor is cooled well enough.
    I think even higher voltages are fine but there hasnt been a lot of feedback of people using high voltages 24/7 so far.

    For extreme cooling there seems to be almost no limit as to what voltage is ok, as long as the cpu still scales, its probably fine
    Last edited by saaya; 03-19-2009 at 03:31 AM.

  2. #2
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    nice thread saaya......I will report quickly...
    Quote Originally Posted by LardArse View Post
    i think you are asking the wrong person about safety limits, but

  3. #3
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    nice thread saaya, looking fwd to see some feedback of 2.0v+ results on C0 after some time

  4. #4
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    Don't think i can adjust that low saaya , 1.1 vtt?

  5. #5
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    very interesting topic

    i think vtt is vcore.
    Core i7 920, Asus Rampage 2 Extreme , 6GB OCZ reaper 15000, EVGA 260GTX SSC, X-Fi Xtremgamer



  6. #6
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    I hope you are wrong AlfaBoy :p
    Question : Why do some overclockers switch into d*ckmode when money is involved

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  7. #7
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    Interesting one... Saaya!
    Can update 2moro tho I hope it stays alive coz I got one more board to finish

  8. #8
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    Quote Originally Posted by AlfaBoy View Post
    very interesting topic

    i think vtt is vcore.

    vtt is qpi voltage, 1.20 is minimum at the p6t and rex2

  9. #9
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    isnt vtt FSB voltage?
    This is my signature, there are many like it but this one is mine..







  10. #10
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    isnt FSB gone?

    I'm running @ 1,85 for 2 day's now... QPI voltage at 1,4v

  11. #11
    Xtreme Owner Charles Wirth's Avatar
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    Up to 2.3v for the past few months on several chips, many many hours.

    No chip degradation, it wants to go faster.

    I have had one on the Vapo for two months now, its at 2vmem

    still scared?
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  12. #12
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    yes.

  13. #13
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    tried that for regular testing..
    vtt : 1.24v
    vcore : 1.48v
    vdimm : 1.84v

    no problem at about 10hours run..

    here what i see from intels datasheet,with a %10 range, i guess pushing vtt to 1.5v and vdimm to 2.1v will not be problem [DO NOT TRY because i said]


  14. #14
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    Sorry for cross posting....but:

    Quote Originally Posted by Astratuner View Post
    ....big snip....Note the most important thing: While Asus and Intel (rightly) scare everyone (read: uneducated) into thinking that 1.65V on the DRAM voltage should be the absolute limit before you reach for the fire-blanket, all that's really needed it to obey this: keep the CPU uncore voltage within 0.5V difference of the DRAM voltage and there's no problem. Over this potential difference and you’ll greatly increase the chance of CPU death, but it certainly won't happen instantly in a big ball of fail fire if you make a mistake.....little snip....
    Can anyone confirm or deny this?

    Quoted from here, page 5, post #120.

  15. #15
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    Chips used: 940/ 2x 965 (all C0 stepping)

    QPIV: ~1.45V (real) all the time.
    VDram: 1.7V-2.05V depending of usage (2.05V is for benching and I used this voltage 15+ hours this weekend)

    Hundreds of hours of basic testing without any problems in past two months.

    I would like to see others post same results, so we can cut the wings of this rumor, which is based on user reports from stepping B era.
    I do know that there is reason for 1.65V limitation and you don't need much more in 24/7 use. Do not go over that limit if you don't feel that you have to.
    That is the most easiest solution and you know that the risk is your own.
    You are as good as your samples are!

  16. #16
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    my87csx481 I'm doubt about
    within 0.5v
    but it is true. My friend told me it after some Intel presentation in Ukraine.
    Last edited by Drager2; 11-17-2008 at 11:54 AM.

  17. #17
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    VTT is the Uncore voltage that powers the L3 cache, memory controller and a part of the QPI controller, plus the integrated power management processor it seems. Default vtt depends on the cpu and is assigned depending on 3 vid pins. It seems to be between 1.1 and 1.2v, though most mainboard makers seem to ignore this and set 1.2v always, which results in up to 1.25v on some boards.

    Quote Originally Posted by FUGGER View Post
    Up to 2.3v for the past few months on several chips, many many hours.
    No chip degradation, it wants to go faster.
    I have had one on the Vapo for two months now, its at 2vmem
    still scared?
    thanks charles,
    roughly how many hours 2.3v have you run and with what vtt?
    and roughly how many hours 2.0v with what vtt?
    This was all below zero though, right?

    Quote Originally Posted by hey View Post
    tried that for regular testing..
    vtt : 1.24v
    vcore : 1.48v
    vdimm : 1.84v

    no problem at about 10hours run..

    here what i see from intels datasheet,with a %10 range, i guess pushing vtt to 1.5v and vdimm to 2.1v will not be problem [DO NOT TRY because i said]

    thanks for posting the pic
    thats the theory, so yes, 2v vdimm should be fine 24/7, but thats apparently only with high vtt.
    Our engineers killed 2 cpus with 1.9v vdimm and stock vtt after just a couple of hours of memtest86+
    then again those were B stepping chips...

    Quote Originally Posted by SF3D View Post
    QPIV: ~1.45V (real) all the time.
    VDram: 1.7V-2.05V depending of usage (2.05V is for benching and I used this voltage 15+ hours this weekend)

    Hundreds of hours of basic testing without any problems in past two months.
    roughly how many hours with 2v vdimm and 1.45v vtt?

    Quote Originally Posted by Drager2 View Post
    my87csx481 I'm doubt about but it is true. My friend told me it after some Intel presentation in Ukraine.
    no offense, but just because your friend heard this at some intel presentation doesnt really make it official

    thanks for the feedback so far guys!
    Last edited by saaya; 11-17-2008 at 07:36 PM.

  18. #18
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    Nice saaya

    My testing so far with boards from Intel Smackover and GIGABYTE X58, always using vdimm 1.8 - 1.95 volt 3 channel, and vtt 1.35 - 1.4, QPI 1.45 mostly setting i used. Using for several weeks until now and looking good.

  19. #19
    Xtreme Owner Charles Wirth's Avatar
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    My notes from another thread.

    vcore ~1.5v, this is a "leaky" high IDV chip, scaling up with higher voltage is possible at a cost of runaway amp phenomena.
    vmem ~2.2v for benching 2v on Vapo, compensate voltage with cooling to be safe.
    vqpi ~1.35v depending on the board/bclock, upwards of 1.55v if I am pushing bclock, I run a low bclock so I usually leave it on stock.
    vmem is the secret to uclk, 2.2v gets you 4.7Ghz ulck. uclk is also known as uncore.

    general ratios

    Stock QPI on i7 965 is x48 @ 133 bclock, if you raise the bclock to 160ish you would need to drop qpi ratio to X44 to continue raising the bclock to 180ish, drop qpi again to X36 again and that will get you out the theoretic max bclock of 220. That is not set in stone, some chips/board combos have exceeded these numbers but this rule is pretty close to what you will see on C stepping.

    The uclk ratio I prefer to use is (the lowest possible) 1:2 of my ram speed (uclk runs at twice the speed of memory) and at lower speeds there are plenty more ratios to scale higher without running the sick memory speeds that I do, this is a huge gain in performance but for me it requires a lot of vmem and high end memory to run upwards of 2300Mhz (4700Mhz uclk) the memory controller has exceptional is its stability at this speed, I have not reached top speed and it will take even faster ram and more vmem to achieve that.

    Runaway amp phenomena, I hook an amp meter to the four yellow wires on eight pin power cable that connects near the CPU. Watching this you will see that yes you can keep scaling up with more voltage but your chip has a limit with all cores loaded that it will runaway on amps till it crashes. I know exactly what range to stay in with cores loaded to know not to hit this runaway threshold. Keeping vcore down and disabling HT lets me run at the chips max speed, HT has an added power load on the CPU, disabling it helps gain critical Mhz.
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  20. #20
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    Maybe raising vtt from 1,1 to 1,2 prevent to kill some i7, when raising the vdiimm, i believe that may exist some combination from vtt and vdimm to prevent killing i7 but isn't easy to now, i which this thread help us

    It is very strange to see max vcore 1,55 in that image, something strange i fond in the P6T is the minimum PLL is set to 1,8 with 920.
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  21. #21
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    nevermind, got my answer.
    Last edited by GAR; 11-18-2008 at 03:54 PM.

  22. #22
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    Cue BenchZOwner's 24/7 2.2v Prime95 marathon.

  23. #23
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    I haven't heard, that there is any dead C0 stepping cpu's. (High Vdram)
    If there is, please tell us how it happened.

    And Sascha.. 2.05V was used 15+ hours in my last weekend bench session. No problems.. nothing. 1.45V VQPI is for 24/7 and memory voltage between 1.8-1.95V.. no signs of problems so far.
    You are as good as your samples are!

  24. #24
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    Quote Originally Posted by Benny Lodewijk View Post
    Nice saaya

    My testing so far with boards from Intel Smackover and GIGABYTE X58, always using vdimm 1.8 - 1.95 volt 3 channel, and vtt 1.35 - 1.4, QPI 1.45 mostly setting i used. Using for several weeks until now and looking good.
    thanks

    Quote Originally Posted by FUGGER View Post
    My notes from another thread.
    so you ran 2.2v vdimm with 1.35v vtt?

    Quote Originally Posted by Gautam View Post
    Cue BenchZOwner's 24/7 2.2v Prime95 marathon.
    yeah looking forward to benchzowners high voltage marathon sessions on i7!
    Quote Originally Posted by SF3D View Post
    I haven't heard, that there is any dead C0 stepping cpu's. (High Vdram)
    If there is, please tell us how it happened.
    nope, havent heard of any at all...

    Quote Originally Posted by SF3D View Post
    And Sascha.. 2.05V was used 15+ hours in my last weekend bench session. No problems.. nothing. 1.45V VQPI is for 24/7 and memory voltage between 1.8-1.95V.. no signs of problems so far.
    ok, thanks!

  25. #25
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    I've been testing my retail i7 920(C0 stepping) + MSI X58 Eclipse for 1 straight week now, I'm using 1.35V VCore, 1.38V QPI Voltage, and 1.85V VDimm,

    No problems so far , still up & running @ 200 x18 for daily gaming use, OCCT CPU test(8 thread load) 30 min passed

    * Well, if there's should be any problem, it's probably the TEMPs, it's so hot that even my Cooler Master Hyper-Z600 with 2 fans(push-pull) only managed to hold the load temps to around 70-ish , I don't know if the Core Temp is faulty, but the Z600 feels hot to touch for me *
    Last edited by Lucky_n00b; 11-19-2008 at 07:30 PM.
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