# Thread: Safe GTL Ref Voltages for 45nm Wolfdale

1. ## Safe GTL Ref Voltages for 45nm Wolfdale

I would like to know what the safe GTL Ref voltages are for 45nm CPU's? (Specifically the wolfdales).

I know how to calculate the voltage from the ratio and vTT, I just want to know the safe voltage for the GTL's.

Also there are settings for Cores (1/3) & Cores (2/4), and my bios says the default for 1/3 is 0.630x and for cores 2/4 default is 0.670x - Why would these be different? Shouldn't both cores be run at the same GTL Ref voltage when using a dual core cpu at stock speeds?

I understand that each core needs to be 'tuned' individually when pushing for max FSB, but shouldn't they initially be at the same GTL Ref voltage?

2. I don't think there is a consensus as to a safe GTL Ref because frankly, there hasn't been that much tweaking of them when overclocking when compared to other settings... the GTLs aren't VOLTAGES, but actually ratios.

3. They are actually voltages

They are derived from the vTT voltage and the ratio.

Eg:

vGTL = ratio x vTT

If GTL Ref Ratio = 0.630x and vTT = 1.12v

vGTL Ref = 0.630 x 1.12v = 0.7056v

Therefore GTL Ref = 0.71v (to 1 decimal place)

4. Have you confirmed this with a multimeter?

5. No, I don't know where to measure GTL Ref voltages on my board. However, the equation that I gave an example of, which is how you derive the GTL Ref voltage, is common knowledge. I don't need to 'prove' it, so to speak.

I just want to know the max safe GTL Ref voltage for 45nm Wolfdales.

6. As i understand it they are indeed not voltages, the best way of describing them could be they are multipliers.

On my blackops the default multiplier (default GTLref) is 0.66x. This is used with the VTT in this way: VTT = 1.35 x 0.66 = 0.891v, which is a value used to determine signal highs and lows (0s and 1s).

If i change a GTLref to +1, i'm actually adding 0.0005 to the 0.66 multiplier. So for my setting of +10, i'm changing the multi from default 0.66x to 0.665x and this would give VTT = 1.35 x 0.665 = 0.89775v, the new reference voltage which is used to determine signal highs and lows (0s and 1s).

Now, as for 'safe' GTLrefs, i'm not sure there is such a thing as an unsafe range. Personally i've tested them extensively on my blackops + QX9650, covering almost the entire range of both minus and positive values, and it hasn't caused any permanent problems with my system like windows corruption or anythinig like that. If you set them too high / too low, you'll not be able to POST, that's all.

7. Yeah, too high or too low and it affects stability. Find the right value and it can lead you to vcore and nb decrease.

8. Ok cheers for that. I know what they give you in bios (ie: 0.630x) is not a voltage in itself, but I meant that the end result of setting them is really setting a voltage that as you said determines signal highs & lows.

9. Originally Posted by CryptiK
Ok cheers for that. I know what they give you in bios (ie: 0.630x) is not a voltage in itself, but I meant that the end result of setting them is really setting a voltage that as you said determines signal highs & lows.

Different bios have different types of settings for them too, i think. On the blackops it's -31 to +31, each step adding or subtracting 0.0005x (i only know this because Shamino kindly divulged it in a thread), whereas on other motherboards it may work differently. I've read of the 790i having up to +50 or -50, though i'm not sure if it's the same difference in each step.

10. Yes, each manufacturer seems to have a different way of giving adjustment. In my asus bios, it has 0.630x/0.670x as stock settings for cores 0/2 and 1/3 respectively.

I don't know why they (each core GTL Ref) would be set differently by default. From what I have read, they *should* both be the same. I have some experimenting to do.

higher GTLs doesnt net anything like raising a vcore value. It is actually very simple with GTLS (unless you have a DFI board like me)

Wolfdale= 61% GTL ref on 0/2 1/3 and NB
Yorkfield= 63% GTL ref on 0/2 1/3 and NB

65nm Dual core= 67% GTL ref on 0/2 1/3 and NB
65nm Quad core=70% GTL ref on 0/2 1/3 and NB (most mobos dont have this option, although I find it to be the best ratio for q6600's)

12. I didnt say that wrong GTLs will result in high vcore. All i just wanted to say is that when you find the right GTL(so 100% stability) you sometime find that you can lower a notch the vcore for example without losing stability.
As for your percentage, my Q9450 likes 64.41%(DFI board) and 67.41% for NB.
Its really a matter of mobo+cpu combination. For DFI i know that 61-63 should be the first values considered, but the NB GTL at DFIs may also want as much as 67%.

13. Originally Posted by SuporterPoli
I didnt say that wrong GTLs will result in high vcore. All i just wanted to say is that when you find the right GTL(so 100% stability) you sometime find that you can lower a notch the vcore for example without losing stability.
As for your percentage, my Q9450 likes 64.41%(DFI board) and 67.41% for NB.
Its really a matter of mobo+cpu combination. For DFI i know that 61-63 should be the first values considered, but the NB GTL at DFIs may also want as much as 67%.
i wasnt specifically adressing you, i meant that you wont get uber leet overclocks by setting GTLs to 85%

14. Originally Posted by SNiiPE_DoGG

higher GTLs doesnt net anything like raising a vcore value. It is actually very simple with GTLS (unless you have a DFI board like me)

Wolfdale= 61% GTL ref on 0/2 1/3 and NB
Yorkfield= 63% GTL ref on 0/2 1/3 and NB

65nm Dual core= 67% GTL ref on 0/2 1/3 and NB
65nm Quad core=70% GTL ref on 0/2 1/3 and NB (most mobos dont have this option, although I find it to be the best ratio for q6600's)
And why these values?

Is this true for any board?

15. Originally Posted by SNiiPE_DoGG

higher GTLs doesnt net anything like raising a vcore value. It is actually very simple with GTLS (unless you have a DFI board like me)

Wolfdale= 61% GTL ref on 0/2 1/3 and NB
Yorkfield= 63% GTL ref on 0/2 1/3 and NB

65nm Dual core= 67% GTL ref on 0/2 1/3 and NB
65nm Quad core=70% GTL ref on 0/2 1/3 and NB (most mobos dont have this option, although I find it to be the best ratio for q6600's)
Right, so there is an optimal setting depending on the class of cpu.

If I set both 0/2 & 1/3 GTL's to 0.610x, I get a lock up on desktop at 4.05 GHz. If I set them both to 0.670x, I can pass 1.5 mins of orthos. I run at 4GHz 24/7 100% stable with the GTL's at 'auto', I'm just experimenting using 4.05GHz as that would fail orthos in less than 30 seconds if I leave the GTL's on 'auto'.

What also confused me was that when on auto, they are apparently set to 0.63x (0/2) and 0.67x (1/3). So you're saying they actually should both be set at the same value?

I'm not playing with them in the hope of gaining any speed, it's just a new board and I don't like leaving things set to auto.

16. CryptiK your board(and from 4days mine too) with the AUTO setting for GTLs sets them at 0.67x.
SNiiPE_DoGG: usually i set the vcore and vnb for a specific vtt value high. After i find the right GTLs that are in accordance with a fixed VTT(VFSB) value then i can back down the vcore and vnb until i loose stability.
As i stated before, the easiest way to explain it is that too high gtl level or too low will cause bsods and freezes. You do not gain stability by increasing their percentage.
Usual values are that written by SNiiPE_DoGG with the mention that they're aproximate, and one should tweak around them.
So example(i did it like this with the Quad and DFI X48):
for a given vtt(vfsb) i put a vcore and a vnb higher than normal so i do know that those arent the causes for instability.
I then knew that the values should be around 61 to 68% from the VTT. With the vtt that i knew i calculated how much 61 would mean in mV and then with a DMM i measured on the board to see how much the actual DFI gtl(for DFI the gtls are numbers like 60-80 so not percentage) is.
You can easily manipulate them because if for example thread #3 in Prime95 is crashing then you know you have to mess with the 0/2(for Asus) and 1/2(DFI) gtl.

17. Originally Posted by CryptiK
I don't know why they (each core GTL Ref) would be set differently by default. From what I have read, they *should* both be the same. I have some experimenting to do.
Yes at default they will be the same.

Originally Posted by SNiiPE_DoGG

higher GTLs doesnt net anything like raising a vcore value. It is actually very simple with GTLS (unless you have a DFI board like me)

Wolfdale= 61% GTL ref on 0/2 1/3 and NB
Yorkfield= 63% GTL ref on 0/2 1/3 and NB

65nm Dual core= 67% GTL ref on 0/2 1/3 and NB
65nm Quad core=70% GTL ref on 0/2 1/3 and NB (most mobos dont have this option, although I find it to be the best ratio for q6600's)
QX9650's prefer 67% actually. That's what i've seen elsewhere, and it's working for me, at least. I'd say Wolfdales prefer 63% more, between 63 and 67.

Originally Posted by SuporterPoli
CryptiK your board(and from 4days mine too) with the AUTO setting for GTLs sets them at 0.67x.
That sounds spot on, most boards as far as i know are 0.67x by default.

18. ok my biostar tp45hp sets them to 63% and 67% default. just read this thread and set them to 61% for both. but there is a option under the cpu gtl and nb gtl that says ISL6322 frequency and it has the options: -15%, -30%, +15%, and +30%. i do not know what this does at all and never touched it. its always set to nominal as that is what the bios says. if somebody knows what that means and explains it that would be great.

19. for my q9650 it only likes 63% exactly, any higher or lower and i freeze on prime.

20. Yeah but roughly we can say that 61-69% is the range to search.