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Thread: P45 boards tries to fry cpu's @ 500FSB? could use some help :)

  1. #1
    Join Date
    Oct 2008

    Default P45 boards try to fry cpu's @ 500FSB? could use some help :)

    I am trying to give my overclock a boost from 3.6ghz to 4ghz, if i get it stable at reasonable voltages.

    I figured out, that on FSB500 the BIOS automatically sets a cpu VTT of 1.6v and a PLL voltage of 1.86v!!!

    Been testing for 2 days on a FSB of 500 with these voltages on auto.
    Guess i can be considered pretty lucky since my chip didnt noticeably degrade / die.
    How is it possible for the BIOS to automatically set these values so far out of the safe range?

    With these voltage on stock (1.5v for PLL and 1.2 for Termination Voltage) i dont seem able to do 500mhz FSB.
    I guess its the PLL voltage is responsable for this?.. does it usually need a bit more for 500FSB?
    Thats where your FSB starts after all.

    I am using 2.00D Strap.
    I have 1.3v on my MCH/Northbridge (where auto sets 1.36), when i hit for 500FSB.
    For current 24/7 overclock on i have 1.2 manually set here.

    Lowered my CPU multiplier to 6 for the moment just to get 500FSB stable first, switched RAM to official rating of 1000mhz @ 5-5-5-18 timings (advanced all auto) with rated 2.1v (will try lower later soon as all is stable).

    I would also like to know what VTT (termination voltage) actually is....
    Is this the setting i know by the term of startup value?...
    just to get your system to post?
    Seems pretty hard to find some clarity about this on the net.
    Really appreciate some explanation on this :)

    Last edited by MadDoGz; 11-11-2008 at 05:38 AM.
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  2. #2
    Lsdmeasap's Avatar
    Lsdmeasap is offline GIGABYTE Guru
    Join Date
    Jan 2008
    PCB Island

    Default Re: P45 boards tries to fry cpu's @ 500FSB? could use some help :)

    I agree VERY MUCH!

    I always suggest PLL for sure be set to stock 1.5 at most any overclock. 1.56 or so may be needed above 500 FSB, but I have ran 543 without it on 45Nm CPU's just fine. 65Nm CPU's did need a slight bump once you got up there though

    And most rest users should manually set/find the Vtt they want to/need use as Auto also overvolts that as well.

    For 45Nm CPU's keep this under 1.38-1.4 for 24/7 use as 1.4 has been known to kill a Quad 45Nm for sure by Anandtech >>>

    1.45 is Intel's rated max for 45Nm CPU's >>>
    intel vtt voltage

    Intel page for doc >>>
    Intel® Core™2 Duo Processor - Technical Documents

    Intel® Core™2 Duo Processor E8000¹ and E7000¹ Series Datasheet (PDF 1.38MB)

    Stock PLL should get you 500 FSB, but you will need more VTT then stock for sure. I have been using 1.32-1.34 for 450 FSB so you may need that or a bit more.

    Here is some reading for you about Vtt and Ref. voltages >>>
    Adjusting A/GTL+ Levels for Increased FSB Signaling Margins and Overclocking - The Tech Repository Forums

    Understanding GTL Reference Voltage]

    CPU And Northbridge GTL Default Settings

    CPU VTT Voltage

    VTT is the termination voltage for data lines used to interface the MCH with the CPU die(s) via the Front Side Bus. Higher values can provide additional FSB overclocking margin, especially with 45nm dual-core processors and quad-cores CPUs in general. We have never found any additional gains to be had above 1.36 when using air- or water-cooling. Setting Auto should default to 1.10V for 45nm CPUs and 1.20V for 65nm CPUs.
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