Just A Warning about High CPU VTT voltage (QX9650 Fried)

Just thought I would post this so everyone could know about the dangers of high VTT voltages with 45nm Intel CPUs. Anandtach referred to VTT voltage as "a ticking time bomb" and they destroyed their 1,000 dollar QX9650 CPU because of the high CPU VTT voltage. They also said they damaged their 9300 quad chip with high vtt as well.

Here is the link: http://www.anandtech.com/weblog/showpost.aspx?i=428

I had my vtt up way too high I realized, after reading this, so I hurried and toned it down. I found I could lower the VTT from 1.5v to 1.4v and it didnt affect my stability, I might try going even lower, I realize that in my testing, when I thought I needed more VTT, I probably just needed more NB voltage. Anyways, just a warning, because it sounds like VTT can kill the 45nm CPUs fast.

what does vtt do?

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Originally Posted by 71 (Bryan)

what does vtt do?

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VTT is also reffered to as the termination voltage, it is used to terminate data lines between the MCH and CPU. But I'm only pretending to know what that means.

upping the VTT on your cpu (if your motherboard has the setting) can result in a more stable overclock. VTT also doesnt seem to increase the heat that a CPU or Northbridge puts off, so many people just upp it to the maximum to be sure it isnt holding them back. Apparently this is dangerous though on 45nm chips.

I thought high CPU PLL killed them as FSB termination on my X38 helps zilch for extra High FSB stability... but looking to hear from other users...

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Originally Posted by Leeghoofd

I thought high CPU PLL killed them as FSB termination on my X38 helps zilch for extra High FSB stability... but looking to hear from other users...

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It couldn't be the high CPU PLL because default specification for PLL on intel quads is 1.5v anyways

Well my Maximus overvolted that PLL voltage with 1.5 bios set to 1.62 and undervolted FSB termination voltage with 0.15... Never needed more than 1.35 FSB term there to get it at 10 x 450 stable... and on the P5K Dlx Pll is always with my CPU's at 1.5... more doesn't help, both CPU's are 465FSB wallers (tested on Maximus SE, eVGA 780i, P5K dlx and Foxconn Mars)

Bump for a good read and some good infos.
Hey, maybe this will also lead to further degradation investigations. Maybe all those degraded chips did not have their vCore too high... but rather... VTT was too high for them! Didn't we have chips recovering from "degradation" with new PSUs? If VTT can destroy or damage the chip when set too high, then the rest of the "degraded" chips could have been caused by this. Didn't we have people running E8400 at 1.34v and their chips still degraded? Thoughts, please?

That's like we all mentioned in the degradation thread : too many factors then just Vcore count here... mobo voltage stability, hardware components used, cooling, user experience,... but this CPU VTT issue is bugging me... will max it around 1.3-1.35 in the future... just to be on the safe side...


So till now max 1.45Vcore and CPU VTT max 1.4 for 24/7 long term stability... what's next Intel ?

vPLL not over 1.60v? I think we might hear that really soon...

Hehehe what's next max 25% OC's ??

just got mine down from 1.6v.... thanks for posting this

What is safe vtt then? I have core i7 920 at 3.8 1600 ram.

vcore is 1.35 and overvolts to 1.38 when stressed.

vtt is set at 1.38 and may overvolt to 1.4 when stressed.

Is my vtt too high? I have watercooling, HKV3

RoEy

VTT ? wat is that I don't even have that 4 a option, guess i should be safe than. :cool:

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Originally Posted by cowpuppy

VTT ? wat is that I don't even have that 4 a option, guess i should be safe than. :cool:

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qpi/dram voltage mate.

Anyone know max safe limit?


I can get to 3.8 but I need 1.38 vtt

RoEy

I7 and 775 limits are completely different... its a different architecture!!!

On P45... 1.55 maybe even 1.60 is fine. On NOT P45.... 1.30

For I7, Id say 1.44v is fine, maybe a bit higher but over 1.50v id advise against for long-term 24/7 use

How much is the max safe 24/7 VTT for a P35 + Q6600 ?

1.4 is no problem for 65Nm and 1.6 PLL