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Thread: Power saving i7 overclocking - QPI and CPU PLL voltage scaling




  1. #1

    Default Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    I am trying to overclock with all power-saving technologies active on my EX58-UD4P/i7 920. What I think this means is leaving voltages at "NORMAL" to allow core voltage scaling to function, but I am wondering what the CPU or Motherboard do to the QPI, CPU PLL, and QPI PLL voltages at idle. If they are scaled down at idle, then it is helpful to keep them on "NORMAL".

    However, if they are always kept constant, then increasing/setting values here would not result in a significant savings and would reduce the restrictions on my overclocking challenge :)

    So do the QPI, CPU PLL, and QPI PLL voltages get scaled down at idle on the i7's just like the CPU Core voltage does??

  2. #2
    Join Date
    Feb 2008
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    54

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    With C1E, EIST enabled at stock/auto settings, only vcore is dropped along with multi and hence mhz, other voltages do not scale down.

    As an aside, since I have been playing with my killowatt meter, I can also tell you how much or little power it saves. The power savings is ~23W on my i7 with EIST/C1E enabled vs disabled.

    My core i7 just the computer itself at stock/auto settings with C1E, EIST enabled draws 231W from the wall at idle. With C1E, EIST disabled it draws 254 watts...so 23W saved. UPS draws 24W, cable + router + speakers draws total of 10W, 26 inch lcd monitor 50W.

    In the grand scheme of things, 20W on a 315W system at rest and 350W gaming, 400W prime load...you will not see much savings (the cpu itself sees a higher percent, but of the whole system not very significant). However if you are being green...if everyone saves 6% it adds up, just you wont notice much on your power bill. And in my overclocked state of 4.2, it draws 370W at idle, 430-450W gaming, linpack 600W.

    On the other hand, using S3 sleep when your not using your computer total watts decreases from 315W to 41W. The computer itself uses 5-7W, rest is from UPS, etc. Now that will show up on your power bill.

    Not that you asked any of that, but I have been playing with my kw meter for past several days and just thought I would share
    3770K 4.7 - Windows 7 64 - GB UD5h - Dom 2133 - corsair 850 - Intel 520 SSD - 680 GTX - 26 inch Samsung LCD
    Lian Li G70 WC

  3. #3

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    I just got a meter also, though I haven't tested it on my new i7 system yet. Besides, the point here isn't to save energy (that's what S3 sleep is for as you mentioned), its just another type of overclocking challenge :)

    Just trying to max performance vs. power now instead of just performance. As long as voltages aren't increased, performance scales up nicely with increased power usage so that's why I want to keep voltages at stock. "NORMAL" keeps the power saving functions on too so why not :)

    Good to know that the other voltages don't scale down. I will pump them up a bit if necessary (highly likely because my QPI is blocking me).

  4. #4
    Join Date
    Feb 2008
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    54

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Gotcha....post some results when you play around with your meter...want to see what other people get.

    As an aside, I get the same 20W power saving when OCed by using EIST, C1E despite the voltage not noticeably dropping in cpuz.

    Also if you OC on auto/normal, your voltages will all go up much more than Ocing on manual voltages. Auto overvolts everything too much when OCing.
    3770K 4.7 - Windows 7 64 - GB UD5h - Dom 2133 - corsair 850 - Intel 520 SSD - 680 GTX - 26 inch Samsung LCD
    Lian Li G70 WC

  5. #5

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Lol doing it right now...brb in 10-15min gotta turn off my computer :)

    Also, the "Normal" setting should not be over-volting at all.

  6. #6

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Here we are (only my box, no accessories):

    C1E/EIST Enabled, higher C states DISABLED:

    Off - 1-2 watts
    Idle - 135 watts +/- 5
    load - 255 watts +/- 5 (Running Prime95 /w 8 workers)
    S3 sleep - 4 watts (very steady)

    C1E/EIST DISABLED, higher C states DISABLED:

    Off - No change
    Idle - 155 watts +/- 5
    load - No change
    S3 sleep - No change

    C1E/EIST Enabled, higher C states ENABLED:

    Off - No change
    Idle - 126 watts +/- 5
    load - No change
    S3 sleep - No change

    I'm at all stock settings right now, no OC. So 20w savings for me also, but 29w savings with higher C states enabled! I noticed my CPU runs 3-4C cooler at idle with higher C states enabled also!

    My setup:
    i7 920 C0/C1 (Stock cooling, turbo enabled)
    EX58-UD4P
    GTX 260 Core 216
    6GB OCZ Ram
    2 Hard drives (7200 RPM)
    1 DVD-Burner
    1 80mm system fan
    Antec Neo HE 550W Power Supply
    Last edited by demonsavatar; 04-20-2009 at 09:12 AM.

  7. #7
    Join Date
    Feb 2008
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    54

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Quite a bit less power hungry than mine by ~100W or so. My ultra is piss poor performance per watt, plus I have 2 water loops with 2 pumps and 9 fans.

    Thanks for posting numbers...interesting to see these i7's can be relatively efficient systems.
    3770K 4.7 - Windows 7 64 - GB UD5h - Dom 2133 - corsair 850 - Intel 520 SSD - 680 GTX - 26 inch Samsung LCD
    Lian Li G70 WC

  8. #8

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Does use of higher C states adversely affect overclocking much? I wonder why the Gigabyte boards come with higher C states DISABLED by default. Free 10w lower idle consumption, and lower idle temps also!

    I'm gonna do some testing with the DES software...

  9. #9

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    Here are some numbers using Gigabyte's DES software. Interestingly the different settings didn't affect my idle power at all. The 1, 2 and 3 setting and CPU throttling on or off all resulted in the same numbers. I waited longer for some of these numbers so I could close the variances a bit to +/- 2 about.

    C1E/EIST Disabled, higher C states DISABLED: Idle - 151 watts +/- 2 (DES does not function without C1E/EIST enabled)
    C1E/EIST Enabled, higher C states DISABLED: Idle - 132 watts +/- 2
    C1E/EIST Enabled, higher C states DISABLED, DES Enabled: Idle - 127 watts +/- 2
    C1E/EIST Enabled, higher C states ENABLED: Idle - 122 watts +/- 2
    C1E/EIST Enabled, higher C states ENABLED, DES Enabled: Idle - 119 watts +/- 2

    More coming soon! I'll keep editing this post...
    Last edited by demonsavatar; 04-20-2009 at 09:15 AM.

  10. #10
    Join Date
    Feb 2008
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    54

    Default Re: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

    I dont think the higher C states or EIST, C1E affect overclocking that much, I havent found any effect once finding stable settings...I know others that have oced have used them...I have not tried yet.

    Be interesting to see what you get with DES software.
    3770K 4.7 - Windows 7 64 - GB UD5h - Dom 2133 - corsair 850 - Intel 520 SSD - 680 GTX - 26 inch Samsung LCD
    Lian Li G70 WC

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