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VTT and GTL ref

Discussion in 'Overclocking & Cooling' started by TheMonkey, Feb 13, 2008.

  1. TheMonkey New Member

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    This was originally posted in motherboards and ram but didn't stir up any information maybe this forum section will be more appropriate...

    So i've been having fun clocking my C2D and have had moderate success so far, but i had a question about VTT voltages and GTL reference. I went ahead and read this article http://www.thetechrepository.com/showthread.php?t=87 but understood very little although it did get me on the right track for tweaking these settings, and thanks to this guide I was able to get my E6750 stable 3.36@1.42v as opposed to 1.45v and saved me a few degrees C. Can anyone give me an explanation of VTT, GTL reference and how they relate in simpler terms? Any insight on these mysterious settings would be great:)
     
  2. trog100

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    the same people read em all dude.. he he he

    no response simple means no one really knows the answer.. we all have google.. just like u..

    trog
     
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  3. TheMonkey New Member

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    U r so right:( no replies...

    I've googled that crap for hours and read everything I can find....maybe someone will chime in one day:eek:
     
  4. Paulieg The Mad Moderator

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    From xtremesystems.org:

    "GTL (Gunning Transceiver Logic) is a reduced swing I/O driver technology support high speed buses and backplanes. Typically it uses a reference voltage derived from the vrm's to establish the swing from 0.4V to 1.2V. If the reference voltage is increased the swing increases and the noise susceptability of the bus decreases.

    The reference voltage is input directly to the cpu and is derived from the Vtt voltage on the vrm's. The intel specs say it is derived from precision 1% resister divider networks but it could also be done other ways as is the case in the rd600 board design.
    There are no pull up or down resisters involved in this circuit (they on on the die itself) so it is unlikely a pencil mod will do anything. On the other hand if a board does use resisters to establish the reference voltage, then maybe it would work.
    This voltage is really critical to the operation of the fsb"
     
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  5. Fitseries3

    Fitseries3 Eleet Hardware Junkie

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    you wont need to mess with the GTL REF voltage unless you are overclocking a quad core CPU.
    the GTL REF voltage can help counter the effects of vdroop under the load of the quad core CPU's. this is an advanced feature and you should FULLY understand how to use it if you plan on changing the default setting. the motherboard bios automatically adjusts the GTL REF voltage when overclocking. there are situations where the bios may improperly set the GTL REF V. and cause the computer not to post. you can lower the value to "trick" the bios into giving the cpu proper voltage under load.

    does that help any? in plain english..... dual core cpu=dont touch(won't really help much)
    quad core cpu=may help at higher clock speeds to get the system stable(450fsb and higher)
     
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  6. Paulieg The Mad Moderator

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    Well said, fit..
     
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  7. TheMonkey New Member

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    Hmm well my dual core is only 3.5 hours orthos stable with stock VTT/GTL settings @ 1.42 volts, but i'm 24 hour orthos stable with my tweaked VTT/GTL settings @1.42v. So it does have some effect on dual core setups as well.... BTW thanks so much for the info Fit/Paul its a confusing subject but you guys are clearing things up 4 me.
     
  8. Fitseries3

    Fitseries3 Eleet Hardware Junkie

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    that is interesting. i haven't seen any impact on dual cores. im not saying i don't beleive you.

    tell me more. im guessing it's your e6750 on the bloodiron?

    im studying to be an electrical engineer... that's how i know a lot of this stuff. although... i don't know everything.
     
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  9. TheMonkey New Member

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    Yep sure is... Without VTT/GTL tweaks I need 1.45v to get 24hour stability @3.36

    Anything higher than 1.3VTT and I lost all stability, I first tried .61GTL @1.3VTT and went from 3.5-->8 hours stable then .57GTL @1.3VTT 8-->24 hours stable
     

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