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Definitive Answer to the .5v Rule on Ivy Bridge QPI/VTT


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#1 wevsspot

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Posted 04 July 2013 - 10:42 AM

Hey guys / gals.

 

In the old days (i.e. socket 1366 / x58) it was widely accepted that the QPI/VTT - QPI/DRAM had to be set within .5v of the DRAM voltage.

 

Is the .5v rule still applicable to socket 1155 and specifically Ivy Bridge?  I've done a lot of online research and the responses I've found range from one end of the spectrum to the other.

 

I'd appreciate it if someone with o/c experience on Ivy Bridge give me some guidance.  I'm completely 4.4Ghz stable @ 1.20v core on this 3770K and it only takes 1.08v on QPI/VTT to get my memory stable at 2133Mhz.

 

But the catch is that my DRAM voltage spec. is 1.65v @ 2400Mhz, however it will happily run at 1.63 - 1.64v for 2133Mhz.

 

Right now the difference in my QPI/VTT is; 1.64v DRAM - 1.08v QPI/VTT = .56v

 

So do you think I'm ok with that difference?  Or, would it be better to set QPI/VTT to 1.14v and keep it within .5v of the DRAM voltage?


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#2 Smiki007

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Posted 04 July 2013 - 11:31 AM

According to intel specs QPI/VTT (VCCIO) max voltage for it is 1.08v some recommends to stay between 1.0-1.1v (for normal/moderate OC), or max voltage of 1.2v (on very extreme memory OC), when you on air or H2O cooling, but either way you can leave it on auto (don't think it would be any difference).

More Info for IB OC en Gigabyte UEFI BIOS

Intel Ivy Bridge Overclocking Guide


Edited by Smiki007, 04 July 2013 - 11:41 AM.


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#3 wevsspot

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Posted 04 July 2013 - 09:09 PM

Thanks Smiki.  I know all of the Intel specs. by heart, but some high speed memory kits (2133Mhz, 2400Mhz etc.) require a slight bump in QPI/VTT that exceeds the Intel spec.  In fact on my 2700K rig I had to run 1.15 QPI/VTT to get 2133Mhz stable at 4.6Ghz o/c on the processor.

 

Mine main question here is for anyone running 1.65 vdimm memory and whether or not the .5v rule still applies to the difference between QPI and vdimm on Ivy Bridge (as some claimed it did on SB, and everyone claimed it did on Nehalem and Bloomfield).


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#4 Braegnok

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Posted 05 July 2013 - 10:30 AM

Good luck on finding a definitive answer, seems everyone I checked with who owns a Gigabyte board has a differant answer. :dunno:  

 

If your stable I would use the lower voltage on the VTT.

 

Your GA-Z77X-UD5H, is a Sweet looking board,.. whats the differance in version Rev.1.0 and Rev. 1.1,.. looks like the LAN 1 8151 Atheros chip for the network port is changed to 8161 on Rev. 1.1 and the Audio/Digital output was upgraded on Rev. 1.1,.. is that all the changes they made.


Edited by Braegnok, 06 July 2013 - 08:27 AM.

      


#5 wevsspot

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Posted 07 July 2013 - 06:16 PM

As far as I know those are the only changes between revision 1.0 and revision 1.1

 

It is a nice board for the most part.  The one thing they missed the boat on is the voltage measuring points.  The points are there, but they are little more than little solder pads that you have to attempt to hold a multimeter on and take a reading.  Much prefer methods such as MSI uses that provide actual headers and small jumper wires that you can actually stick a probe into.

 

Overclocking the 3770K was a snap though.  Straight to 4.2Ghz on stock voltages and everything on Auto.  Then went right to 4.4Ghz with just an offset voltage change to allow for 1.19v cpu core, QPI/VTT to 1.08v with low load line calibration on both.  So far I'm happy  :)

 

As suggested I went with the low QPI/VTT.  Since I wasn't getting much feedback here, I popped in over at another forum and caught the advise of some folks with a lot of experience with this board and similar variations.


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