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  1. #1
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    i7 940 stuck at 3.8 ghz

    I am pulling my hair out here, I have an i7 940. Don't hate on it I got it really cheap! And I am running on a p6t with a Coolit domino, I see all of these people getting sick OCs on i7 920 and all that but mine seems to hit a wall at 3.8 Ghz. It is not at all thermally limited, it idles at 36 to 37 degrees. I can get it to passmark cpu test at 3.9 but it is not at all Prime95 stable. I am looking to run this 24/7 at the highest clock speed I can muster with my current set up, while trying to keep idle temps under 40 C. I am a nut but I just really want my 940 to beat a Xeon 5650 and I am darn close 7070 pts to Xeons 8070pts, I'm within spitting distance to an opteron too, 8203 pts.

    Here's my rig:
    Coolermaster 840 ton's of air flow
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    Coolit Dominoe using decent thermal paste
    i7 940 at 3.8 Ghz 200 x 19

    Vcore 3.5
    Pll1.9
    QPI/Dram 3.5
    1.1 ich 1.1 ioh
    LL enabled

  2. #2
    Member Gabkicks's Avatar
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    try turning pll down to 1.82, unless you know you nee 1.9. try raising ioh and ich to 1.2 vtt and making sure ram timings are stable. i need a lot more voltage to hit 4ghz than 3.8.
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  3. #3
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    Can you give more details? Motherboard make and model?

    Also, Im assuming your vcore is 1.35v? Definitely need more ICH (VTT) voltage. IOH really wont matter much, you can bump it but I doubt the IOH will help any if at all. Whats your uncore ratio? It should be twice your DRam multiplier (DRam is running 8x multi in your case, uncore should be 16x).
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  4. #4
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    Most 940s were C0 and many would have difficulty reaching 4GHz....

    If you're not thermally limited, then why are you only running 1.35V (assuming that's what you meant)....some chips need much more....try 1.4V, 1.45V, etc.... as long as your temps are in check your CPU might need the extra

  5. #5
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    Yes I am running 1.35 volts sorry for the typo. I have tried higher voltages, I got up to 1.375 and I couldn't even squeeze out 205 on the BCLK. The memory is fairly stable, I ran these clocks and timings at 1790 mhz when I was at a lower BCLK. The motherboard is an Asus p6t. I have the unclock on auto which just doubles the ram clock as far as I understand.
    My cpu tends to hate higher multipliers too, at 19 it's rock solid and cool but at 20 or 21 it can't handle much over 150 BCLK. I'll take it through a few runs with the recommended settings and get back to you. What doe sICH control and why would I want to raise it? Thanks for the help, this is my first i7 build.

  6. #6
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    I am running a 920, and I had a similar issue back in the day... really, 1.35v to 1.375v is not that big of a jump to go anything over 3.8, from what your telling us. my chip "comfort level" before it hits the "wall" for 4.0 is 1.34v, but if i raise it to 4.1 or 4.2, i need a whole lotta more voltage. seems that 1.35v is where your voltage curve will sharply raise for any faster speeds you desire. ie.: 1.34v for 3.6 and 1.35v for 3.8, but if you go 4.0 you will need a .1 raise, rather than a .0275 raise... like 1.4 or 1.45v

    So, with the much higher voltage jumps for the smaller increase in speeds you will run a lot hotter. What do your temps max at? idle doesn't matter to much, but its good, low idle temps sometimes means lower max temps when it gets up but not always. Anthing over 70-72c for 24 prime95 test is my max. but thats just me, i am on water and it hovers about 65-67...

    I need to reaserch your specific chip a little more... been "away" since April, and I am sure with the speed of technology they have 15 core processors and 6000gb ram chips! LOL!
    Last edited by Norcalsteve; 09-06-10 at 11:31 AM. Reason: repeated a question: removed one
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  7. #7
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    Thanks for looking into it guys and gals. I tried a run at 40 ghz with 1.4 vcore and I raised ich to 1.3 I took qpi drma down to 1.82 and it seems to be stable at 3.8. I tried 1.4 and I got a few BSODs,

    I tried 20x200, 21x191, 22x182, and 23x174. 23x174 booted but it was too hut for my taste, 53 degrees on the cores. 21x191 booted but would not pass prime95.

    I think I am going to try a run at 21x195 to see if there is a "hole" in the performance. then try upping the voltages a little bit to get stability at 21x191.

    Any tips? 1.4 vcore still gives me idle temps under 40, which I am happy with and that is with load line leveling enabled.
    Is it possible to go a little higher with vcore than that and turn off LLL to get better temps?

    PS I just finished trying to get to 4ghz and i managed to get through a run of passmark 8300 points on the processor. Now I want to make it stable even more! I tried all the way up to 1.45 vcore and QPI/dram at 1.4 still no stability. Any chance it might just be a big "hole" in performance? Do you think I should just go balls to the wall with 4.2 Ghz? I read that the new i7s don't really have "holes" per se, holes were caused by bad mobo chipsets and the ineteraction between the fsb and the cpu.
    Last edited by sharpsuxx; 09-06-10 at 12:15 PM.

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  9. #9
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    Hi Sharpsuxx! Welcome to the OC Community!

  10. #10
    Member Killador's Avatar
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    Quote Originally Posted by sharpsuxx View Post
    Thanks for looking into it guys and gals. I tried a run at 40 ghz with 1.4 vcore and I raised ich to 1.3 I took qpi drma down to 1.82 and it seems to be stable at 3.8. I tried 1.4 and I got a few BSODs,

    I tried 20x200, 21x191, 22x182, and 23x174. 23x174 booted but it was too hut for my taste, 53 degrees on the cores. 21x191 booted but would not pass prime95.

    I think I am going to try a run at 21x195 to see if there is a "hole" in the performance. then try upping the voltages a little bit to get stability at 21x191.

    Any tips? 1.4 vcore still gives me idle temps under 40, which I am happy with and that is with load line leveling enabled.
    Is it possible to go a little higher with vcore than that and turn off LLL to get better temps?

    PS I just finished trying to get to 4ghz and i managed to get through a run of passmark 8300 points on the processor. Now I want to make it stable even more! I tried all the way up to 1.45 vcore and QPI/dram at 1.4 still no stability. Any chance it might just be a big "hole" in performance? Do you think I should just go balls to the wall with 4.2 Ghz? I read that the new i7s don't really have "holes" per se, holes were caused by bad mobo chipsets and the ineteraction between the fsb and the cpu.
    Whats your QPI/DRAM set to? This is a very sensitive setting and i think you changed it from auto... is that correct?
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  11. #11
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    I do have the QPI/Dram at 1.35, I have read many posts that have their QPI at 1.4 for 4 ghz+ OCs. with Load Line leveling I am stable at 3.8ghz with 1.35 and 1.35 respectively. I would love to turn off LL and get stable at 4ghz+. I have read a few place though that the 940 d0s are not quite as stable overclockers as the 920s and 930s, i am going to try 1.4 qpi and 1.3 vcore and see whats up.

    Using the OCing guide I got to 200mhz Bclock and found that I could run my multi up to 19 at my current voltages. Now I am just trying to coax the last few mhz out of it.

  12. #12
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    That is very respectable for a 940 (which is likely a C0 by the way) I have to believe if there are any 940 D0's that are in circulation they're probably ES
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  13. #13
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    I always assume that if I can boot at a certain frequency I can run stable at it somehow but beyond 3.8 it just doesn't seem possible. The p6t is a rock solid board but I can't seem to get the 940 to boot windows past 3.8ghz.

    I have tried all kinds of iterations and no dice. I think the 940 has a problem OCing because it is basically just a failed 965 that they didn't want to throw away. I mean it has a 23x multi which should be great, but it just hates to run that high.

    My OC temps are actually cooler than stock temps at the 23x multi. I will continue to fight though the wall and any help will be greatly appreciated to get me out of OCers block, lol. It might just be that 3.8ghz is as high as i can go, I had a lot of luck with my old e6300 I got it to go 3.0ghz when it was stock 1.86. I guess 3.8 may just be the practical limit for my i7 940, damn you intel and spoiling my fun!!!

  14. #14
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    Quote Originally Posted by sharpsuxx View Post
    I think the 940 has a problem OCing because it is basically just a failed 965 that they didn't want to throw away. I mean it has a 23x multi which should be great, but it just hates to run that high.

    My OC temps are actually cooler than stock temps at the 23x multi.
    3.8 is a typical limit for a C0 chip. To go further, the voltage needs to jump drastically. Think 1.4V+ CPU VCore, as well as VTT. Temperature is more closely related to your Voltage. You should not be experiencing higher temperatures at a lower clock speed and lower voltage. If you are, then something is incorrect with your HSF mounting.
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  15. #15
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    So is VTT, qpi/dram or IOH I heard it referenced both ways. Does voltage have anything to do with how high multi you can run? I can run up to a 23x multi so theoretically I can try some different iterations of Bclk. Does multi or bclk have a greater affect on stability?

    I only ask because I see so many people running 200 bclk instead of a lower bclk and a higher multi.

  16. #16
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    Quote Originally Posted by sharpsuxx View Post
    So is VTT, qpi/dram or IOH I heard it referenced both ways. Does voltage have anything to do with how high multi you can run? I can run up to a 23x multi so theoretically I can try some different iterations of Bclk. Does multi or bclk have a greater affect on stability?

    I only ask because I see so many people running 200 bclk instead of a lower bclk and a higher multi.

    CPU VTT = QPI/DRAM. The only reason it would allow you to run a higher multi or limit your multi is if you were not supplying enough voltage for the projected speed.

    200 Base Clock is very desirable, as it allows perfect correlation with popular Ram speeds. 200 bclk, 20 multiplier (on a 920/930, 21 with turbo), and 2:8 ram ratio. Gives you 4ghz on the CPU (4.2 with turbo) and a perfect 1600 mhz on the RAM. If you have 2000 mhz Ram, simply bump the Ram ratio to 2:10.

    Stability at that base clock will be dependent on a few things (your board and your CPU primarily) Most newer 1366 boards (of decent value) have no trouble hitting 200+ bclk. Some of the original boards showed some weakness in this area. Whether or not your CPU can do 200 bclk is another issue. Newer D0 chips... no problem... 940 C0 @ full multi... no way. The higher multiplier allows you just that many more options for configuration. Stability will be dependent on Voltage more than anything else.

    Possible Configurations for 4ghz:
    211 bclk x 19, 2:8(2:10) Ram = 4009 mhz CPU, 1688(2110) mhz Ram
    200 bclk x 20, 2:8(2:10) Ram = 4000 mhz CPU, 1600(2000) mhz Ram
    191 bclk x 21, 2:8(2:10) Ram = 4011 mhz CPU, 1528(1910) mhz Ram
    182 bclk x 22, 2:8(2:10) Ram = 4004 mhz CPU, 1456(1820) mhz Ram
    174 bclk x 23, 2:8(2:10) Ram = 4002 mhz CPU, 1392(1740) mhz Ram
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  17. #17
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    Ok, still stuck at 3.8 but the good news is I can enable speed step and all the C states at 3.8ghz. I have tried this bad boy all the way up to 1.45 vcore and 1.4 vtt, I just dont feel comfortable going much higher. I got it to boot into windows at 4.0ghz at 1.45 vcore but I had to use the 23x multi settings which for some reason makes my cpu all kinds of hot or triggers the sensors to malfunction or something. In speed fan the CPU temp is only 36 but the core temps are like 53???

    I feel like since I am so rock solid at 3.8 that I must be able to hit 4 somehow. I still feel stuck!! But at least with turbo my passmark cpu score is now just under 8000, its 7937 instead of 7885, yay .5% improvement!!!
    Last edited by sharpsuxx; 09-14-10 at 10:22 PM.

  18. #18
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    So I finally gave up and sold my 940 bought a 950. Great move on my end, the i7 950 I bought runs at 4.2ghz all day at good temps.
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  19. #19
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    Quote Originally Posted by sharpsuxx View Post
    So I finally gave up and sold my 940 bought a 950. Great move on my end, the i7 950 I bought runs at 4.2ghz all day at good temps.
    And now you see the difference between C0 and D0 Congrats man
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  20. #20
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    Yeah after the thermal settled a little bit it got a bit hotter, are tighter screws on the heatsink going to cool it down or heat it up?? I never know when to stop torquing my heatsink screws??
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