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Thread: wtf is fsb termination voltage anyway?

  1. #1
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    wtf is fsb termination voltage anyway?

    does anyone have a good answer?
    in my experience, increasing it prevents the cpu from missing clocks, but i have no idea how it works or anything.
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    o rly i have it set tp 1.5 on mine seemd to make pc more stable when i unlocked multi and ramped up FSB

    but yer i dont really have a clue wat it does
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  3. #3
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    All I know is that I went from an instant BSOD, to a flash of the windows loading screen and then a BSOD after pumping up the FSB Termination voltage...so yeah it seems to do a tad bit of something
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    maybe its the voltage of the FSB itself...
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    it doesnt seem to do anything for me

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    source -> line -> component -> short line -> termination

    the "lines" in this case are signal traces. works a lot like a SCSI bus. high speed switching operations can cause reflections on the line (in essence, this is resonant noise caused from high-speed switching on the lines as the memory controller gates on and off to place data on the bus, nothing more than rising and falling voltages). clearly enough, the faster the signal switches (higher frequency memory) the more noise.

    termination resistors, used in passive termination environments, are exactly matched to the target frequency for operation based largely on trace length, ESR (equivalent series resistance) and the over capactive/inductive nature of the circuit, as well as some other things well out of the scope of this post. problem is that this is often matched for a specific frequency...which as we know is not so cool for overclockers. enter the active termination system. this actually uses a voltage bias to set final line resistance value so that the user can tune for better operation when overclocking.

    this method of tuning is largely trial and error as you have no way of know the specification of the circuit or have any idea of the calculations need to find the "perfect" value. so anway, the answer is, strangely enough, whatever works best.

    hope this helps.

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    holy cow now THATS and answer the demands some respect!!
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    Im sorry to bump up this old thread, but is there a limit whichi should stay within, or can i just rape my Wolf with 1.5-1.6V FSB termination voltate?

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    Quote Originally Posted by nullface View Post
    Im sorry to bump up this old thread, but is there a limit whichi should stay within, or can i just rape my Wolf with 1.5-1.6V FSB termination voltate?
    I believe for the 45nm parts Intel has a safe range of 1.045V < 1.10V <1.155V (higher for 65nm parts) but there are those that are running as high as 1.30V--I am running @ 1.16V for 400FSB. If you go to their sight you should be able to find the data sheet pertaining to your chip that gives the safe limits for both vtt and PLL.
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  11. #11
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    45nm = 1.15v max, 1.45v absolute max. Going above the max may immediately cause irreparable damage, and the functionality nor reliability of the CPU can no longer be guaranteed. I prefer to stay under the stated 'max' of 1.15v.
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  12. #12
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    1.26v if you are using Intel '4' series chipset - according to Intel: http://download.intel.com/design/pro...hts/318732.pdf
    Last edited by thehinge1; 08-18-2008 at 09:44 PM. Reason: eta: per thei published 'safe' settings, I stay@1.30 or less
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  13. #13
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    Quote Originally Posted by CryptiK View Post
    45nm = 1.15v max, 1.45v absolute max. Going above the max may immediately cause irreparable damage, and the functionality nor reliability of the CPU can no longer be guaranteed. I prefer to stay under the stated 'max' of 1.15v.
    As far as I'm concerned, the default FSB Termination Voltage by Intel is:

    1.1V for the 45nm parts
    1.2V for the 65nm parts

    As for what's safe and what's not... the maximum voltage of 1.45V doesn't seem to be the real maximum anyways ( at least 3 of my Core 2 Duo's 45nm disagree ) [ and I will be putting even more CPUs to the test, and even higher voltages ]

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    should 1.2vtt be considered high then? what about a p45 NB whats considered high over 1.3v ??

    I am getting 518x8.5 stable on a e8600 and it takes 1.2vtt and 1.26 on the NB.
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    Quote Originally Posted by Rattle View Post
    should 1.2vtt be considered high then? what about a p45 NB whats considered high over 1.3v ??

    I am getting 518x8.5 stable on a e8600 and it takes 1.2vtt and 1.26 on the NB.
    I really don't see it being necessary to exceed 1.3V on the NB for the p45 chipset. I hit 450FSB using 4x1GB of RAM >1100MHz on a quadcore w/ only 1.24V, so unless you are just seeing how high you can go for benching >1.30V shouldn't be needed. The same also applies to vtt, I don't really see why 1.2V would be necessary for a 24 hour clock IMHO.
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    Just remember there is also such a thing as TOO high. Setting the FSB VTT to 1.4 assuming that'll cover you for any kind of overclock is wrong.

    There is too low and too high. And I don't think anyone needs 1.4 as I can do 4.25ghz on 1.2V so .. unless you're on LN2, start with 1.2 and work slightly up/down from there

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    Quote Originally Posted by CryptiK View Post
    45nm = 1.15v max, 1.45v absolute max. Going above the max may immediately cause irreparable damage, and the functionality nor reliability of the CPU can no longer be guaranteed. I prefer to stay under the stated 'max' of 1.15v.
    thats the reference VTT not the max, the max is usually near the max rating for the core

    but intel no longer lists it on their spec sheets
    Last edited by zanzabar; 08-19-2008 at 10:43 AM.
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