How to set up GTL Ref Values for 45nm & 65nm

For a good explanation of what GTL Ref voltages are and do, go here:

http://www.thetechrepository.com/showthread.php?t=87

I will simply explain how to set them for your particular CPU and motherboard. They are very important for quad core cpu's, but also affect the stability of dual core cpu's.

A GTL Ref voltage is derived from the Vtt (vFSB) voltage. The GTL voltage is a certain percentage of the Vtt so to set it you use a multiplier (eg: 0.667x) which means the resulting voltage is 0.667x (66.7% of) the Vtt voltage.

For 45nm CPU's, on boards where you just set the multiplier, you should begin with the 0.635x multiplier for each core, and for 65nm CPU's, you begin with the 0.667x setting for each core. From there you tweak as necessary to find the optimum sweet spot for you cpu & FSB.

Some new boards (like Maximus II Formula) use a different method for setting the GTL Ref voltages. They do not simply have a multiplier, the multiplier remains fixed and you enter a 'Y value' that modifies the resultant voltage.

If you have a 45nm cpu, you are aiming for the voltage given by the 0.635x multiplier, so to work out what to put for the the 0.667x GTL Ref (Y) values (it will be a negative number to make the resulting voltage the same as the 0.635x GTL Ref voltage), use the following eqn, but substitute the Vtt you use, in place of the example Vtt.

In the examples given, I have rounded off to 3 decimal places throughout for simplicity.

For me, Vtt = 1.14v

Equation:

Vtt x 0.667 + Y = Vtt x 0.635

1.14v x 0.667 + Y = 1.14v x 0.635
0.760v + Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

So to verify it:
1.14v x 0.635 = 0.724v
1.14v x 0.667 = 0.760v

0.760v - 0.036v = 0.724v

or an easier, non algebraic alternative:

1.14v x 0.635 = 0.724v
1.14v x 0.667 = 0.760v
0.724v - 0.760v = -0.036v
= -36mv

Round up to the nearest selectable bios value, in Maximus II Formula bios this is -40mv

So now you set the 0.667x 'Y value' to -40mv

You have now made the 0.667x GTL voltage as close as possible to the 0.635x GTL voltage.

If you have a 65nm cpu, you are aiming for the voltage given by the 0.667x multiplier, so to work out what to put for the the 0.635x GTL Ref (Y) values (it will be a positive number to make the resulting voltage the same as the 0.667x GTL Ref voltage), use the following eqn, but substitute the Vtt you use, in place of the example Vtt.

For me, Vtt = 1.14v

Equation:

Vtt x 0.667 = Vtt x 0.635 + Y

1.14v x 0.667 = 1.14v x 0.635 + Y
0.760v = 0.724v + Y
Y = 0.760v - 0.724v
Y = 0.036V
Y = 36 mv

So to verify it:
1.14v x 0.667 = 0.760v
1.14v x 0.635 = 0.724v

0.724v + 0.036v = 0.760v

or an easier, non algebraic alternative:

1.14v x 0.667 = 0.760v
1.14v x 0.635 = 0.724v
0.760v - 0.724v = 0.036v
= 36mv

Round up to the nearest selectable bios value, in Maximus II Formula bios this is +40mv

So now you set the 0.635x 'Y value' to +40mv

You have now made the 0.635x GTL voltage as close as possible to the 0.667x GTL voltage.

**EDIT**

Naming and meaning of the CPU gtl ref's, and land pin assignment names (Kindly provided by Mikeyakame):

CPU GTL Reference (0/2 Lane0/Lane2)
GTL Reference Data Strobe Input Buffer Middle/End Landing Pins 0 & 2. (GTLREF0/GTLREF2)

CPU GTL Reference (1/3 Lane1/Lane3)
GTL Reference Address Strobe Input Buffer Middle/End Landing Pins 1 & 3 ( GTLREF1/GTLREF3 )

For quad-core multi-die chips:
Middle Landing Pins (GTLREF0/1) act as input buffer for DIE0, End Landing Pins ( GTLREF2/3 ) act as input buffer for DIE1.

For dual core single-die chips:
Middle Landing Pin (GTLREF0/1) acts as input buffer for DIE0, End Landing Pin (GTLREF2/3) uncertain if used. Either unused and terminated to open drain Vtt or used as reference for middle pins as margin of error.

Things to note concerning adjustment:
Address strobe Pins (GTLREF1/3) will generally tolerate small variance with respect to reference voltage accuracy, and should in most cases be setup a little lower with respect to Data strobe Reference multiplier or voltage.
Why?
Probably the same reason as any other reference or input voltage for clock strobes, signal resonance or cross talking.

Data strobe pins (GTLREF0/2) will not tolerate being out by more than 0.5-1% below nominal, but will tolerate slightly more above nominal. Keep set values above Address Strobe GTL multiplier/voltage offset.
Why?
Works better in almost all situations, don't know why until I get a chance to monitor on a logic analyzer.
By How Much?
Varies according to FSB base clock, higher the FSB BCLK the smaller the difference will probably need to be at least with respect to the Diff Amplitude driving the clock.

Also not that when you are adjusting the GTL Refs with a board that using a fixed multiplier and a modifier (eg: +/- in mv) the resultant Vref will be slightly different for the data strobe lanes and the address strobe lanes, as shown by this example (Kindly provided by Seban):

Calculations made for a Vtt = 1.365v

GTL Ref 0 = +50mv = 0.9336025v
GTL Ref 1 = +10mv = 0.9381305v
GTL Ref 2 = +50mv
GTL Ref 3 = +10mv

GTL Ref 0 = +30mv = 0.9136025v
GTL Ref 1 = -10mv = 0.9181305v
GTL Ref 2 = +30mv
GTL Ref 3 = -10mv

As you can see, the resulting Vrefs are not quite equal, but they are close enough for the sake of GTL Ref adjustment. The aim is not to have the Vrefs all exactly the same, but to find the GTL Ref settings that give you the most stability.

**EDIT 2**

Attached to this post is a spreadsheet kindly made by Seban, allowing easy calculation of GTL Refs required, as a starting point fo your tweaking. Here is his description of it:

I got little present for every one for new year .

It is simple Excel file which is counting GTLs and NB GTL as well as new Multiplier for you and few other minor values for given Vtt. It is nothing special but saves time and allows to tweak GTLs without asking for help and getting too much into it.

How to use it:

First type in desired / currently used vtt voltage as in your bios (or rather the way it looks loaded in Everest for example - but bios one is also working fine)

Secondly put some correction numbers and watch how GTL values are changing (Max and Min values of GTL for given VTT are also shown there).

The goal is to figure out which GTL works best for you for one VTT - in most cases the same GTLs voltages will work for different VTTs or very similar ones (or sometimes not ). So when we switch Vtt we would need to adjust GTLrefs to values which will give same or close to same GTLs as working previous ones for different vtt.

Anyway have fun using it, I created it to make my life easier and it does the job.

PS. There are 2 sets of values to compare between different VTT.
PS2. This calculator is made for MF2 board but will work with all boards that got correction number in equation (like +40 or - 20 and so on).

Quote:

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Originally Posted by CryptiK

For 45nm CPU's, on boards where you just set the multiplier, you should begin with the 0.635x multiplier for each core

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I read this elsewhere too, but people i've talked to seem to generally be going for 0.67x for the QX9650 / Q9450.

Nice write up :)

my QX9650 is liking -50mv on cores 0 & 2....that's even a bit lower than the 0.635 that's recommended. If I let it at 0.67 then it isn't as stable.

Quote:

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Originally Posted by CryptiK

For me, Vtt = 1.14v

Equation:

Vtt x 0.667 - Y = Vtt x 0.635

1.14v x 0.667 - Y = 1.14v x 0.635
0.760v - Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

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Your algebra is wrong there in the first part. You lost the negative sign with the Y... it should be +36mV, not negative.

Thanks for trying to explain, but after reading it through 10 times, I'm still left confused :confused:

I will keep at it...

Quote:

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Originally Posted by Polizei

Your algebra is wrong there in the first part. You lost the negative sign with the Y... it should be +36mV, not negative.

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I have way oversimplified this for ease of explanation. The answer is in fact -36mv for the 0.667x Y value, but I was debating about how to show that. I thought the way I wrote it showed more clearly what had to be done rather than be mathematically perfect.

This is correct mathematically, but I thought having '+Y' in both equations may confuse people:

Equation:

Vtt x 0.667 + Y = Vtt x 0.635

1.14v x 0.667 + Y = 1.14v x 0.635
0.760v + Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

I have changed it now in the first post.

Something still isn't right.

At first, you were subtracting a negative, which made it positive. Now you are adding a negative, which is negative.

Maybe I'm just going nuts. :confused:

EDIT:

Yours:
1.14v x 0.667 - Y = 1.14v x 0.635
0.760v - Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

Mine:
1.14v x 0.667 - Y = 1.14v x 0.635
0.760v - Y = 0.742v
- Y = 0.742v - 0.760v
Y = -0.742v + 0.760 [multiple both sides by -1 to remove the negative sign infront of Y]
Y = 36mv


When you subtracted the 0.760 from both sides, you seem to have dropped the negative sign infront of the Y. As long as it's corrected in the first post, fine by me... just making sure we are both on the same page. I hope it doesn't seem like I'm trolling... I just want to make sure I understand this Vtt stuff too because P45 is confusing the hell out of me. I went from 975x to P45... big jump.

@ CryptiK

It is very easy to see that you are wrong...
Your formula is:

Vtt x 0.667 = Vtt x 0.635 + Y

Can't you see that there isn't a solution for that equation, when Y=0?
And I can set it to 0 if I want to on my board.

No, you are mathematically correct in your statement, I did drop the minus in front of the Y. What I meant is, it should have been expressed as

Vtt x 0.667 + Y = Vtt x 0.635

1.14v x 0.667 + Y = 1.14v x 0.635
0.760v + Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

But I expressed it deliberately incorrectly as

Vtt x 0.667 - Y = Vtt x 0.635

1.14v x 0.667 - Y = 1.14v x 0.635
0.760v - Y = 0.724v
Y = 0.724v - 0.760v
Y = -0.036v
Y = -36 mv

I did it like that initially in an attempt to make it clear that when setting up for a 45nm cpu, you must put a negative number (eg: -40mv) for the 0.667x multiplier Y value. However I think it would be better to express it as I have now, which is using a '+Y' in each of the examples, and it is now mathematically correct. Thanks for the feedback, it was clear what I was doing & why in my mind, but it's good to know that it would be better to just express it mathematically correctly rather than the way I had it initially.

Here's the corrected example with full working:

Vtt x 0.667 + Y = Vtt x 0.635

1.14v x 0.667 + Y = 1.14v x 0.635
0.760v + Y = 0.724v

subtract 0.760 from both sides of the equation

Y = 0.724v - 0.760v

Y = -0.036v
Y = -36 mv

Make sense now?

Quote:

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Originally Posted by Cable_Tie_Guy

@ CryptiK

It is very easy to see that you are wrong...
Your formula is:

Vtt x 0.667 = Vtt x 0.635 + Y

Can't you see that there isn't a solution for that equation, when Y=0?
And I can set it to 0 if I want to on my board.

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Of course there is no solution to the equation when Y = 0, but that is not the point of this. We must solve the equation for Y. What I am doing is showing you how to find the appropriate value for Y to adjust the voltage produced by 0.667 x Vtt to yield as close to the voltage produced by 0.635 x Vtt, how to adjust the voltage produced by 0.635 x Vtt to yield as close to the voltage produced by 0.667 x Vtt.

On your board if you put 0 for Y, you are not adjusting it at all, you have just the multiplier x Vtt, eg: 0.635 x Vtt + 0 = 0.635 x Vtt

All fine and dandy but not all boards have a CPU VTT.

My Biostar Tpower I45 doesn't have it unless I'm blind and missed it somewhere in the crazy amount of bios settings.

Quote:

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Originally Posted by firebane

All fine and dandy but not all boards have a CPU VTT.

My Biostar Tpower I45 doesn't have it unless I'm blind and missed it somewhere in the crazy amount of bios settings.

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It's there, labeled FSB Voltage: http://enthusiast.hardocp.com/image....8xOF9sLmdpZg==

Quote:

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Originally Posted by Singh400

Thanks for trying to explain, but after reading it through 10 times, I'm still left confused :confused:

I will keep at it...

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I'm with you on this :confused::confused:

Anyone want to dumb it down a bit more?

Thanks Cryptik

I use .61ref on CPU to my Q6600 on my P35 board and .67red to the NB, seem to go up well on that values, achieved stable what it's on my sig

Cheers mate
Sergio

So in reality if I am getting this correctly, the Equation is for the Newer boards like the Formula correct? I think thats why my brain is twisted in a knot now. :)

Larry

thanks for the write up man...hope it would be as easier now.

Quote:

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Originally Posted by Big Lar

So in reality if I am getting this correctly, the Equation is for the Newer boards like the Formula correct? I think thats why my brain is twisted in a knot now. :)

Larry

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Yes the equation is what some boards like the M2F use, rather than just the multipliers. If you just have the multipliers, start with 0.635x for 45nm and 0.667x for 65nm, it's as simple as that.

It's only on the boards where they give you the Y value to modify that you need to use the equation to work out the appropriate Y value.

Intel spec specifies all 45Nm and 65Nm desktop chips XE and non-XE use the same GTLREF[3:0] multiplier values. It's Motherboard manufacturers that don't follow the specs possibly due to design?

This is taken from the processor specification documentation for the 45Nm QX9770.

Interesting, as I could find no such reference to AGTL+ bus voltage definition in the e7000/8000 data sheet.

So to simplifier you take your FSB Termination Voltage (VTT) and multiple it by whatever increments you have for GTLs, right?

IE:

45nm:
VTT x GTL increment = GTL Refs

1.22 x 0.635 = 0.7747

Or have I got that completely wrong?

Quote:

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Originally Posted by Philly_Boy

my QX9650 is liking -50mv on cores 0 & 2....that's even a bit lower than the 0.635 that's recommended. If I let it at 0.67 then it isn't as stable.

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Blackops X48 seems to love 0.67x, at least it's working for us over at the quantum force section. ( http://www.xtremesystems.org/forums/...d.php?t=201022 )

I guess it must depend on the mobo, which i thought was wrong... But i can't think of anything else.

I'm running my EVGA 750i FTW with pencil mod. I have 1.31825V in BIOS & 1.304V under load and idle in Windows. This voltage is enough for 3,825 GHz (8,5x450). So with adjusting GTL Ref values I should be able to hit higher clocks at lower voltage, right? Mine FSB VTT is 1.20V in BIOS and 1.18V in Windows (at least Everest say's so...).

Quote:

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Originally Posted by mskvorc1

I'm running my EVGA 750i FTW with pencil mod. I have 1.31825V in BIOS & 1.304V under load and idle in Windows. This voltage is enough for 3,825 GHz (8,5x450). So with adjusting GTL Ref values I should be able to hit higher clocks at lower voltage, right? Mine FSB VTT is 1.20V in BIOS and 1.18V in Windows (at least Everest say's so...).

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Yes provided you raise VTT you should be able to. it's dependant on the VCore voltage, FSB frequency and VTT voltage. GTL reference voltages vary for different input and output voltages. The curve is not linear by far. What ratio or extra millivolts might work great for one vCore and one VTT might be out of range for another. It's alot of trial and error mostly. Look at that graph on the Techrepository article for FSB frequency vs GTL reference voltage and make sure you understand clearly what is happening. It will save you many hassles believe me. GTL reference voltage adjustment has the capacity to fine tune vCore and FSB frequency, along with NB voltage, but also has the same capacity to send your system haywire from bounce or jitter.

Quote:

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Originally Posted by Philly_Boy

my QX9650 is liking -50mv on cores 0 & 2....that's even a bit lower than the 0.635 that's recommended. If I let it at 0.67 then it isn't as stable.

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It not cores 0 & 2. It has nothing at all to do with cores. 0 & 2 means GTLREF[0] (GTLREF_ADD_MID) and GTLREF[2] (GTLREF_ADD_END) which are address bus clocking low/high reference land pins. 1 & 3 means GTLREF[1] (GTLREF_DATA_MID) and GTLREF[3] (GTLREF_DATA_END) which are data bus clocking low/high reference land pins. They are for each die respectively. 0 & 1 feed die0 and 2 & 3 feed die1. It's possible I have them back to front, but I'm pretty sure this is the correct order.

Quote:

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Originally Posted by CryptiK

Interesting, as I could find no such reference to AGTL+ bus voltage definition in the e7000/8000 data sheet.

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Aye we are all here to help each other. I don't think any other spec datasheet lists the GTLREF voltage specs besides the QX9000 one. I haven't seen it in any other datasheet at least.

Quote:

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Originally Posted by Singh400

So to simplifier you take your FSB Termination Voltage (VTT) and multiple it by whatever increments you have for GTLs, right?

IE:

45nm:
VTT x GTL increment = GTL Refs

1.22 x 0.635 = 0.7747

Or have I got that completely wrong?

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You are correct if you just have the option to set which multiplier is used, and the resultant GTL+ Ref voltage is Vtt x GTL Increment.

Quote:

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Originally Posted by mikeyakame

Aye we are all here to help each other. I don't think any other spec datasheet lists the GTLREF voltage specs besides the QX9000 one. I haven't seen it in any other datasheet at least.

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Thanks mate yeah I just checked through and only found it mentioned there. I actually run my e8400 at 0.667x as I find it is more stable. I find it strange they don't mention it elsewhere.

Thanks for fielding the other questions too.

This looks like a useful thread, although I still don't understand it fully after reading it several times! How exactly should I set my GTL voltages? Details of my current settings are below. If there's any way I can use less vCore or get a slightly higher OC with the same vCore as I'm using, that'd be awesome.

CPU Voltage [1.4250] (real = 1.408 under load)
CPU GTL Reference (0/2) [Auto] (Defaults to 0.630x)
CPU GTL Reference (1/3) [Auto] (Defaults to = 0.670x)
CPU PLL Voltage [1.54]
FSB Termination Voltage [1.20]
NB Voltage [1.26]
NB GTL Reference [Auto] (Defaults to = 0.630x)

Any help on this would be appreciated. Sorry for the n00b post, I never had to deal with these settings when I was using AMD!

You just have the multipliers to set so that is easy.

Start by setting both to 0.635x - if this is unstable, increase them one increment at a time until it's stable. I run mine at the equivalent of 0.667x and can run vcore one notch lower, so you may need to set ~0.670x for both of them. It's trial and error to find your cpu's sweet spot.

Generally higher vcore, and higher VTT you can run lower gtlref multipliers depending on clock frequency and multi for cpu. Setting the right GTL reference voltages is all just trial and error. Adjust VTT and adjust the GTLREF multiplier opposite of each other is what I usually do. If I modify VCore without modifying VTT then I adjust the GTLREF multiplier slightly higher, where as If I modify VTT without modifying VCore I will adjust it lower. Same goes for NB voltage, if the bios has NB GTLREF multiplier adjustment, you need to fine tune it when you modify vNB or vTT.

One other thing that I'll mention is. I always keep vTT higher than vCore. This might sound weird to most but it is actually how vTT is designed to work. It acts as a buffer for vCore during overshoot mainly during power on. If it is actually lower than vCore then there is a higher risk you can damage a CPU from too high vCore. It is also basically a limiter for valid BCLK high. IE. I run 1.43v vCore on my Q6600 G0 and 1.42V vTT in my Rampage bios (which is actually 1.47V vTT when loadline is enabled on my particular board).

Yes thats true, I use a (comparatively to most) low Vtt of 1.16v so I use higher GTL+ Ref.

Quote:

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Originally Posted by CryptiK

You are correct if you just have the option to set which multiplier is used, and the resultant GTL+ Ref voltage is Vtt x GTL Increment.

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Well I've got both my GTLs set tp 0.635 and it's running fine. Don't really see a need to increase it. TBH still trying to get my head round it all.

Quote:

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Originally Posted by Singh400

Well I've got both my GTLs set tp 0.635 and it's running fine. Don't really see a need to increase it. TBH still trying to get my head round it all.

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Yeah only change it if you adjust vTT , if its on auto leave GTLREF on auto. You shouldn't adjust GTLREF at all unless you manually set vTT and vNB.

I wish I could get my head around this stuff. I still have no clue.

Quote:

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Originally Posted by Dee

I wish I could get my head around this stuff. I still have no clue.

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:D Don't worry if you cant get your head all the way around it, it takes time and practice. Lots of reading too! There are still some things I don't have my head completely around because I never bothered to my finish studying my engineering degree! The best way to understand how it plays a role in your system is to try making bios changes gradually and run tests like Linpack, Prime95, Everest etc while watching voltages through Rivatuner, Everest, HWMonitor, etc to get a feel of how different changes affect your setup.

It's one of those things where if you try and understand it without applying it you will end up confused!

I'll try and draw up a 2D or 3D graph in Autocad for you guys to explain it better and create a pdf of it. Ideally i'd like to be able to show the relationship between AGTL+ reference voltage and the associated voltages / limits such as Crossing Voltage, Crossing Point, Min and Max Thresholds, vIL, vIH, Overshoot, Undershoot, FSB SWING, Rising / FAlling edges of BCLK0/BCLK1, BCLK (FSB Base clock), and anything else I can manage to explain visually.

Thing is, I feel these extra settings I know nothing about could be limiting my overclocks. I have possibly the worst E8600 on here. 4.33GHz for 1.40v? That's rubbish compared to pretty much every other E8600 in the database. I would love a real OC pro to set up my BIOS and see what the CPU is actually capable of. Right now, I'm fumbling through it. Having been an AMD person for the last 4 years I guess it's gonna take some time, but man it's quite frustrating at times!

Quote:

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Originally Posted by Dee

Thing is, I feel these extra settings I know nothing about could be limiting my overclocks. I have possibly the worst E8600 on here. 4.33GHz for 1.40v? That's rubbish compared to pretty much every other E8600 in the database. I would love a real OC pro to set up my BIOS and see what the CPU is actually capable of. Right now, I'm fumbling through it. Having been an AMD person for the last 4 years I guess it's gonna take some time, but man it's quite frustrating at times!

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Don't beat yourself up so bad, with time and trial you'll figure out what your particular board and chip likes. You also need to play with Memory Dividers and vPLL they can assist you as well.

OK, I'll keep tweaking. Thanks Mikey.

Good post!

I found a real easy way.

VTT = 1.20v (use a nice clean number for ease of math);


To get

VTT * 10 = 12v

Now change v to mv. 12mv = 1%.

So to go from 67% to 63%, you want -12*4=48mv

To go from 67% to 61% you want -12.5*6=72mv

I find this to be easy enough to calculate in my head on the fly using this shortcut method.

Of course, that's assuming GTLVref is 67% as anandtech states rather than .667 by default.

Quote:

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Originally Posted by mikeyakame

One other thing that I'll mention is. I always keep vTT higher than vCore. This might sound weird to most but it is actually how vTT is designed to work. It acts as a buffer for vCore during overshoot mainly during power on. If it is actually lower than vCore then there is a higher risk you can damage a CPU from too high vCore. It is also basically a limiter for valid BCLK high. IE. I run 1.43v vCore on my Q6600 G0 and 1.42V vTT in my Rampage bios (which is actually 1.47V vTT when loadline is enabled on my particular board).

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Doesn't this then limit the amount of Vcore you can use on 45nm parts? If Intel says that the max vtt is ~1.155V and the Vcore needed for say 3.8GHz is 1.31V (LLC enabled), wouldn't that put out of spec for vtt?

What is more dangerous a high vtt or a high PLL?

I can get 3.8GHz stable (9.5x400) w/ the following settings w/ hardware in sig:
CPU Voltage: 1.31875 (LLC enabled)
CPU PLL: 1.53975V
FSBT: 1.23250V
DRAM: 2.10
NB: 1.23250V

CPU GTL (0): Auto
CPU GTL (1): -45mV
CPU GTL (2): Auto
CPU GTL (3): -45mV

So by what you were saying it would be better for me to increase my vtt to at least 1.32V to help buffer overshoot even though I am stable at a lower vtt?

Also, I don't remember where this was posted in this section, I had read that you want to keep your vtt as close to your NB voltage as possible for stability, was that statement wrong?

Max instanteous vTT is generally the same value as max instaneous vCore +- 5-10%. Intel doesn't recommend over 1.45V continuous vTT on 45Nm parts which is funnily enough the same soft limit for vCore continuous voltage. The buffer effect is why vTT should be soft limited to no more than the maximum safe vCore. A little over won't kill the chip as long as you compensate with a little less vCore

Maybe this would help. I made this for my reference when I had my QX9650 on the S2E.

http://img100.imageshack.us/img100/8...tgtldr9.th.jpghttp://img100.imageshack.us/images/thpix.gif

I wish I could say it helps but I'm just as confused now as I was before I started reading this thread! Nothing makes sense, or I'm too stupid to understand...

Quote:

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Originally Posted by mikeyakame

Max instanteous vTT is generally the same value as max instaneous vCore +- 5-10%. Intel doesn't recommend over 1.45V continuous vTT on 45Nm parts which is funnily enough the same soft limit for vCore continuous voltage. The buffer effect is why vTT should be soft limited to no more than the maximum safe vCore. A little over won't kill the chip as long as you compensate with a little less vCore

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Okay, where does Intel recommend no more than 1.45V vtt and by soft limited are you referring to what is actually set in the BIOS? Also, when you speak of "max instantaneous" vtt are you telling me that vtt actually fluctuates from the set value during power-on or a switch from low to high load?
Not trying to pick your statement apart but just trying to understand your choice in words.

Quote:

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Originally Posted by Dee

I wish I could say it helps but I'm just as confused now as I was before I started reading this thread! Nothing makes sense, or I'm too stupid to understand...

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I will try to explain. As Everybody has stated, the Intel specs say that quads have a reference GTL of 66.7% or 67%(hence the 0.667 or 0.67) of VTT/vFSB. But for some reason, even if the board gives the GTL voltages as per Intel's reference numbers, the chips are not stable.I don't want to go into "Who's fault is it anyway?" game between the mobo manufacturers or Intel. Remember, this only happens @ high FSBs with the quad.So to make the chips to be stable you think it's the Vcore and increase the Vcore, but still end up with an unstable chip and also unnecessary heat. That's the reason a lot of us with our experience with playing around with GTLs can give you a reference point like saying the 45nm quads seem to be stable with less of a GTL than the refernce of 67% of VTT.

Now, going into the calculation, let's say your rig is semi stable with a VTT of 1.30V. According to the reference from Intel, if you leave the GTLs @ auto, it will give the GTLs exactly that(0.667 times 1.3). But, for 45nms you want your GTLs lower than that. So you determine that you have to give negative values for the GTL so that board will give 0.667 times VTT-xx where -xx is the amount that you actually set in the BIOS of different boards. That's why when you see in my spreadsheet, I had put Auto as zero. Now the question is what does the -xx amount that you would have to specify in the BIOS. It's a simple math calculation. If you want to give a GTL of say 0.657, you are reducing the reference GTL by -0.01. So for a VTT of 1.30V, the equation becomes 1.3x-0.01x1000 = -13mV. The x1000 is because it's in milli volts.For a GTL for 0.647, you go 1.3x-0.02x1000 and so on and so forth.


Sorry about the long post. Hope this helps.

Great explanation, heck even I understood that for once :) Thank You.

Larry

Quote:

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Originally Posted by tekjunkie

I will try to explain. As Everybody has stated, the Intel specs say that quads have a reference GTL of 66.7% or 67%(hence the 0.667 or 0.67) of VTT/vFSB. But for some reason, even if the board gives the GTL voltages as per Intel's reference numbers, the chips are not stable.I don't want to go into "Who's fault is it anyway?" game between the mobo manufacturers or Intel. Remember, this only happens @ high FSBs with the quad.So to make the chips to be stable you think it's the Vcore and increase the Vcore, but still end up with an unstable chip and also unnecessary heat. That's the reason a lot of us with our experience with playing around with GTLs can give you a reference point like saying the 45nm quads seem to be stable with less of a GTL than the refernce of 67% of VTT.

Now, going into the calculation, let's say your rig is semi stable with a VTT of 1.30V. According to the reference from Intel, if you leave the GTLs @ auto, it will give the GTLs exactly that(0.667 times 1.3). But, for 45nms you want your GTLs lower than that. So you determine that you have to give negative values for the GTL so that board will give 0.667 times VTT-xx where -xx is the amount that you actually set in the BIOS of different boards. That's why when you see in my spreadsheet, I had put Auto as zero. Now the question is what does the -xx amount that you would have to specify in the BIOS. It's a simple math calculation. If you want to give a GTL of say 0.657, you are reducing the reference GTL by -0.01. So for a VTT of 1.30V, the equation becomes 1.3x-0.01x1000 = -13mV. The x1000 is because it's in milli volts.For a GTL for 0.647, you go 1.3x-0.02x1000 and so on and so forth.


Sorry about the long post. Hope this helps.

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OK, I think I'm starting to get it. I'm running an E8600, btw. I have two GTL options in my BIOS, (0/2) which defaults to 0.63, and (1/3) which defaults to 0.67. What starting point would you recommend for tweaking these? vTT doesn't usually exceed 1.26v. I also have NB GTL reference which I leave at Auto. I would love to OC my CPU higher but it needs lots of vCore (1.4v for 4.33GHz, which is below average for this chip).

Err let me try again. It's damn confusing to explain but here we go.

There are two particular GTL Reference voltage values you need to be concerned with. These are NB GTLREF and CPU GTLREF. They are two difference reference voltages for two differential clock waveforms occurring seperate of each other. They both have similar purposes but for different clock signals. There are other GTL Reference voltages but these don't have any play on overclocking really, there is only one common factor between all of them, and that is vTT. vTT is the common termination voltage used for CPU, NB, CMOS and PECI GTL+ values which they all need to operate under to work correctly.

NB GTLREF affects the Reference voltage point for the FSB Clock Waveform.
CPU GTLREF affects the Reference voltage point for the CPU Clock Waveform.

Any changes made to vTT must reflect on both NB and CPU GTLREF values. CPU GTLREF isn't effected nearly as much and its minimum Low and High Input voltages are fairly close to GTLREF, they are 100mV or 0.1V off GTLREF. There is a 0.2V swing from low to high and high to low, and provided that the lowest point of the differential waveform doesn't occur within the swing range you are safe.

NB GTLREF on the other hand which negates FSB validity is much less tolerant to differential waveform minimum points. It requires a lower multiplier ratio at higher vTT to maintain the minimum low and high input voltage values.

I need to sit down and try and figure out a simpler way to explain this so you guys can make sense of it. I'll continue this post soon. Need to make a coffee and clear my mind with some C++ code writing.

Thanks Mike. To be honest, I'm almost ready to give up on GTL tuning. I appreciate the explanations, though.

I've been reading this thread and I still don't understand this: What do I want my values to be?

-My E8500 C0 needs 1.32v to post at 4.5ghz, but it needs over 1.5v to be 3D-bench-stable at 4400mhz

-9.5x463 is just as stable as 8.5*517, so the instability shouldn't be because of the ram,
because both mem and the mobo's FSB pass SuperPI at 550mhz, and are IntelBurnTest-stable at 533.

Max suicide-shot on 1.40v is 4609mhz @ 9.5 x 485
and on 1.56v 4662.4mhz @ 9.5 x 490.8
so I don't think its about vcore holding it back, something else is wrong or its just a crappy chip ;(

My current 24/7-values are as follows:
7.5x533 ~4005mhz 1.36v (one step down and it won't pass IntelBurnTest), GTLREF on auto
ram on 533mhz 1:1 5-5-5-15 @ 2.21v
NB on 533mhz, 1.47v (one step down and it won't pass IntelBurnTest), GTLREF on auto
My vFSB, of VTT if you will, is 1.26v
and my vPLL is 1.55v

I'd be interested in lovering my vcore 24/7, and achieving more maximum CPU frequency as well as bench stability past 4400mhz. The NB doesn't even get hot to the touch so I guess its fine as it is. I'm running a Asus P5E Deluxe with the Rampage Formula 0408 bios

Since a few days I replaced my E8400 with a E8600 (Q822A435, VID 1.21v) due to a lack of OC possibilities. According to the batchnumber this should be a great CPU to OC. However I'm having difficulties to get things stable. I think it could have something to do with GTL settings. In general I understand to principal after reading thetechrepository.com and some other site.

I found that I can boot to 610FSB with everything on auto settings, except for dynamic read / write and spread spectrums. I want 450FSB to get my DDR3 to run at 1:2 divider. With still everything on auto I can boot into Windows and CPU-z reports 1.32v but it is far from stable with orthos. I started fiddling around with VTT, vNB and higher vcore (up to 1.41v in bios) without much succes.

Help would be much appreciated.

Quote:

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Originally Posted by Dee

OK, I think I'm starting to get it. I'm running an E8600, btw. I have two GTL options in my BIOS, (0/2) which defaults to 0.63, and (1/3) which defaults to 0.67. What starting point would you recommend for tweaking these? vTT doesn't usually exceed 1.26v. I also have NB GTL reference which I leave at Auto. I would love to OC my CPU higher but it needs lots of vCore (1.4v for 4.33GHz, which is below average for this chip).

---

I got the same options in my bios but how the hell did you find out what your default GTL values are? And how high your VTT really is?

Quote:

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Originally Posted by tekjunkie

I will try to explain. As Everybody has stated, the Intel specs say that quads have a reference GTL of 66.7% or 67%(hence the 0.667 or 0.67) of VTT/vFSB. But for some reason, even if the board gives the GTL voltages as per Intel's reference numbers, the chips are not stable.I don't want to go into "Who's fault is it anyway?" game between the mobo manufacturers or Intel. Remember, this only happens @ high FSBs with the quad.So to make the chips to be stable you think it's the Vcore and increase the Vcore, but still end up with an unstable chip and also unnecessary heat. That's the reason a lot of us with our experience with playing around with GTLs can give you a reference point like saying the 45nm quads seem to be stable with less of a GTL than the refernce of 67% of VTT.

Now, going into the calculation, let's say your rig is semi stable with a VTT of 1.30V. According to the reference from Intel, if you leave the GTLs @ auto, it will give the GTLs exactly that(0.667 times 1.3). But, for 45nms you want your GTLs lower than that. So you determine that you have to give negative values for the GTL so that board will give 0.667 times VTT-xx where -xx is the amount that you actually set in the BIOS of different boards. That's why when you see in my spreadsheet, I had put Auto as zero. Now the question is what does the -xx amount that you would have to specify in the BIOS. It's a simple math calculation. If you want to give a GTL of say 0.657, you are reducing the reference GTL by -0.01. So for a VTT of 1.30V, the equation becomes 1.3x-0.01x1000 = -13mV. The x1000 is because it's in milli volts.For a GTL for 0.647, you go 1.3x-0.02x1000 and so on and so forth.


Sorry about the long post. Hope this helps.

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The thing is boards do not give just 0.667x for all GTL Ref's when left on auto. They give 0.635x for GTL Ref (0/2) and 0.667x for GTL Ref (1/3).

There are a few mathematical ways of working this out, just do whatever works for you. Your equation is fine. I gave the equation in the format in the first post as that is what is given in some bioses. When you just have the multipliers (0.635x, 0.667x etc), just choose whichever one you want and you're done.

This is a hard thing to explain, understanding how AGTL+ signals work can be tricky, but tuning them is the easy part, but for an inexperienced overclocker, it is something best left alone. To understand them properly you just need to do a bit of reading first.

In most cases for average overclocks, you are fine to just leave them on auto, and as always, if you don't understand what a setting in your BIOS means, don't touch it.

Quote:

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Originally Posted by Pisklink

I got the same options in my bios but how the hell did you find out what your default GTL values are? And how high your VTT really is?

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The BIOS tells me what the default GTL values are. I'm not sure about what the "real" vTT is, I can only go on what I set in the BIOS to be somewhere near accurate.

@ Dee

How does it report that to you, through hardware monitor or something? Now I'm curious if I could assume if my board has the same default values as yours?

My BIOS gives a brief explanation for each setting in a little pane on the right side of the screen. It tells you basic info, like the standard voltage a certain option is set to, or how raising a certain value may allow better overclocking... that kind of thing. Next to the GTL settings it tells me that one is set to 0.63x and the other is set to 0.67x when on Auto.

Here you go. Sorry about the blur, camera is a bit crap.

http://img518.imageshack.us/img518/9312/gtlgs8.gif

Thanks for the screenie!!!! I got the exact same Bios layout as I can see from the picture. Ofcourse I noticed this pane on the right side but never noticed this standard value. When I'm home I will take a look if both standard GTL settings differ for my board too.

would have been some great info if only DFI had defined the GTLs as a multiplier of vTT instead of the values they're using which has no relation to a multiplier or voltage... :down:

I'm still a bit confused on all of this, but from what I get from everything here's how I set mine:

FSB Voltage: 1.50v
Processor: Q6700
Motherboard: Evga 750i FTW

Equation:

1.50v x 0.667=1.50 x 0.635 + Y
1.001v=0.953v + Y
Y = 1.001v - 0.953v
Y = 0.048v
Y = 48mv

From this, I set all GTL Ref's to the closest number to 48mv, which was 50mv for my board. Presuming I did the math correct, is this right?

Quote:

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Originally Posted by Hamilton

would have been some great info if only DFI had defined the GTLs as a multiplier of vTT instead of the values they're using which has no relation to a multiplier or voltage... :down:

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You have to go to the spreadsheet that they link to in the BIOS tuning manual and then convert in a much more complex way than has been discussed here! A real PITA and I'm an engineer (the stuff here is is really basic for me)! It wouldn't be bad if the spreadsheet had equations in it, but someone has replaced the equations with just numbers so you don't have the underlying formulas and you have to do intermediate extrapolations from their subtables. :shocked: At least they could have left the formulas. In fact, they could have had it just compute the numbers for you! Who ever did the original sheet had everything needed.

Quote:

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Originally Posted by Hamilton

would have been some great info if only DFI had defined the GTLs as a multiplier of vTT instead of the values they're using which has no relation to a multiplier or voltage... :down:

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As stated by davidk21770, refer to the linked table. I have no idea why companies seem to want to make it harder for you to work out. I have tried to keep it as simple as humanly possible in this thread.

Quote:

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Originally Posted by Baleful

I'm still a bit confused on all of this, but from what I get from everything here's how I set mine:

FSB Voltage: 1.50v
Processor: Q6700
Motherboard: Evga 750i FTW

Equation:

1.50v x 0.667=1.50 x 0.635 + Y
1.001v=0.953v + Y
Y = 1.001v - 0.953v
Y = 0.048v
Y = 48mv

From this, I set all GTL Ref's to the closest number to 48mv, which was 50mv for my board. Presuming I did the math correct, is this right?

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Yes, you are correct :up:

Quote:

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Originally Posted by mikeyakame

Generally higher vcore, and higher VTT you can run lower gtlref multipliers depending on clock frequency and multi for cpu. Setting the right GTL reference voltages is all just trial and error. Adjust VTT and adjust the GTLREF multiplier opposite of each other is what I usually do. If I modify VCore without modifying VTT then I adjust the GTLREF multiplier slightly higher, where as If I modify VTT without modifying VCore I will adjust it lower. Same goes for NB voltage, if the bios has NB GTLREF multiplier adjustment, you need to fine tune it when you modify vNB or vTT.

One other thing that I'll mention is. I always keep vTT higher than vCore. This might sound weird to most but it is actually how vTT is designed to work. It acts as a buffer for vCore during overshoot mainly during power on. If it is actually lower than vCore then there is a higher risk you can damage a CPU from too high vCore. It is also basically a limiter for valid BCLK high. IE. I run 1.43v vCore on my Q6600 G0 and 1.42V vTT in my Rampage bios (which is actually 1.47V vTT when loadline is enabled on my particular board).

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I went in and decoded the DFI spreadsheet to guess at some GTL values for my MB (see sig) and my system is definitely stabler on that next OC that I'm working towards.

BUT, if I increase VTT to even close to Vcore, I don't even post. Are you suggesting that I need to reduce GTL to get the same thresholds that I have for the working VTT? Do you have an example?

SOmething along those lines. If you change the vTT voltage and use the same GTLREF multiplier you would be increasing GTLREF also since it follows vTT.

If you are using 0.67x multiplier for example or 67% of a 1.30v vTT, that gives a GTLREF voltage of 0.87v. Lets say you increase vTT to 1.60v, since GTLREF follows vTT, you would now have a GTLREF voltage of ( 1.60 * 0.67 ) or 1.072v. The problem with this is that GTL reference voltage needs to be generally between 0.8-1.0v max. ANy higher and you generally end up with a situation where the NB can't figure out what is and what isn't a valid clock wave. In other words the end result worst case scenario is, no valid clock wave = no post since the NB doesn't understand what is and what isn't a clock signal.

So say I was aiming around 0.95v GTLREF at 1.60v vTT, I would need to reduce the Multiplier down to 0.59x or decrease the voltage by 0.12v or -120mV to get back to that point. This is just an imaginary value and generally you wouldn't need 1.60v vTT unless you were using over 1.60v vCore and 1.60v vNB.

THe idea of adjustable GTL Ref voltage is to be able to find a fine balance between the relationship of vTT, vCC / vCore, vNB, and most importantly to be able to raise or lower the voltage ranges where a valid clock wave occurs for both logical high and logical low waveforms. If you don't understand those it's not all that important, just remember that clock waveforms occur when you apply power to the circuit, then one clock later when you switch the circuit back to ground. Sometimes theres jitter, noise, cross chatter, and other electrically related phenomenons that disrupt or deform the clock waveform. Changing the voltage at which the reference for all other voltages in the system follow can move the clocks waveform into a region where previously the clocks waveform deviated from its wave path, you move the points at which the readings are taken. It's something like telling day and night apart during long days. The only way to differentiate is by the sun and moon but since there is heavy cloud where you are standing and you have no watch for all you know it might be night even though it looks like day. You move yourself from where you are to where the clouds arent, and doing this you know if its the sun or moon in the sky, thus if its night or day. GTL reference voltage adjustment isn't all that more complex than that for somebody who doesn't need to understand all the science and maths behind it. Moving it enough sometimes you get a clear enough sky to operate normally!

Quote:

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Originally Posted by mikeyakame

So say I was aiming around 0.95v GTLREF at 1.60v vTT, I would need to reduce the Multiplier down to 0.59x or decrease the voltage by 0.12v or -120mV to get back to that point. This is just an imaginary value and generally you wouldn't need 1.60v vTT unless you were using over 1.60v vCore and 1.60v vNB.

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Are you saying that VTT should be as high as the lowest setting. In my case for example, I'm using the following in bios settings:

- 460 x 9.5 = 4.3Ghz
- CPU 1.4v
- CPU PLL 1.58v
- VTT 1.3v
- vNB 1.55v

With these settings the CPU was stable for 9 hours in othos. But when I increased RAM speed to 1840Mhz I thought it needs more vNB and increased it to 1.57v and 1.61v but now it fails after an hour. Could this have something to do with a low VTT?

Well Intel spec says it should always be greater than vCC / vCore but in real world this isn't always necessary. From what I can figure out from the little actual explanation Intel gives about relation of vTT to vCC, it appears that in all cases vCC tracks vTT, where vTT is -+0.10v of vCC for that chip. Possibly vCC tracking vTT is for something along the lines of additional noise immunity for the signal, the tracking effect would limit the electrical potential between vCC and vTT, and if I understand this correctly the smaller the potential difference that exists the greater the effect of vTT being able to shield the vCC signal from noise which becomes somewhat critical as frequency increases. The immunity also works both ways, limiting the amount of noise leaked into other signals.

Quote:

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Originally Posted by Pisklink

Are you saying that VTT should be as high as the lowest setting. In my case for example, I'm using the following in bios settings:

- 460 x 9.5 = 4.3Ghz
- CPU 1.4v
- CPU PLL 1.58v
- VTT 1.3v
- vNB 1.55v

With these settings the CPU was stable for 9 hours in othos. But when I increased RAM speed to 1840Mhz I thought it needs more vNB and increased it to 1.57v and 1.61v but now it fails after an hour. Could this have something to do with a low VTT?

---

Adjusting the NB voltage close to CPUPLL can potentially result in leakage into the closed internal PLL voltage. The larger the gap between CPU PLL and any near by voltages the better usually. It's extremely touchy when it comes to noise or leakage and will destabilize the CPU eventually. If you raise NB to 1.61, take CPU PLL to around 1.68V at the sensor, vTT to 1.38 - 1.42 at the sensor, NB GTLRef if you have a multiplier aim around 0.56-0.62, and then you might be ableto bring vNB to around 1.57v. That is what I would start doing, and see what response I get and play from there. It's not scientific calculation or anything like that! Those voltages all respond in some what of a particular manner when taken that high. It'll be hard to stabilize the system your best bet might be to drop the performance level by 1, and bring the NB voltage down a little, the farther the gap between the NB voltage and vCC and the higher vNB is, the more difficult it becomes to keep the whole system from cross chatting and phases on data/clock/address signals keeping aligned with internal skew adjustment values.

The RF I have behaves similarly too, as have other Asus X48 boards I've played with. It becomes too difficult at a point where vNB is really high to compensate across the other values to keep the system from doing random and odd things. 1.59-1.61v NB on mine I found was about the limit before random behaviour plagued the system, cross chatter or noise related. This was only with 1.50v vTT, and I didnt really want to push it much higher since I didn't have enough headroom on vCC to keep going. That was PL6 pulled in to PL5 on phases a1/a3/b1/b3,333 strap and 1160mhz ddr2, and timings very tight, latency around 48ns.

Mike, i just wanted to post and say thanks for taking the time to explain this to others so that they may benefit.

Top Class, for sure!

Excellent info Mike, thanks, that brings a lot of what I have read elsewhere in bits and pieces together more cohesively. It sure is nice to have an trained engineer around :up:

Mike thank you so much for your explaination. I read quiet a lot with regard to GTL on the techrepository.com and edgeofstability.com websites. However its described very theoretical and its in English which makes it hard to follow when it's not your native language. I think I understand you for the biggest part.

But I thought I read somewhere that the harm VTT can cause is very underestimated and that it should be treated with care because it can seriously damage your CPU. That is why I'm somewhat suprised to hear you say that it may be as high as vcore. I think there are only a few that use this knowledge when you would ask people here on the forum if there VTT value is nearly the same as there vCC.

At this particular moment I have the following OC result which is 4 hours stable on 4.4Ghz.

- Vid = 1.2375
- Strap 333Mhz
- Vcore = 1.4125v in bios
- CPU PLL = 1.58v
- VTT = 1.28v
- vNB = 1.55v
- LLC = auto
- Spread Spectrums disabled
- Dynamic read / write disabled

http://img300.imageshack.us/img300/2070/44cputt2.th.jpghttp://img300.imageshack.us/images/thpix.gif

Now I want to increase RAM speed to 1860Mhz. I always thought that it would need extra vNB to reach that speed. But this is wrong according to your explanation because the gap would be larger between vNB and vCC. Moreover when I start finetuning vCC eventually the gap would become even bigger. I think I'm not able to run RAM at 1860Mhz with above settings (I will try ofcourse). Should I try lowering PL or should I add GTL and try to get voltages at the required distance from eachother to prevent destabilizing?

better to use dual cores with maximus formula / rampage formula because of the gtl adjustment overlook... what is your opinion on this?

i use a q6600 on my RF and its perfectly fine, i run it at 3.45ghz for every day stuff with 430MHz FSB and 8x multiplier. I never went to a 45nm quad core chip because personally the benefits of sse4.1 can't be utilized all that much yet since not much code has asm optimizations added to use the extra registers. I run 1.43-1.44v through it 24/7 and it hasn't missed a beat for the last 15 or 16months. If you want really high clocks definitely go for a dual core, but I've found a quad core running at 3.4-3.6ghz is much faster for compiling, encoding and even simultaneous drive defragmenting than a dual core even running at > 4.5GHz could ever be. In other words if you don't need the full use of a quad core, you will probably see more benefits from a higher clocked dual core. It has nothing really to do with gtl or anything else, the VRM on the MF/RF struggles at 500MHz FSB for a quad core, so if 500Mhz FSB and up is your goal then either of those boards aren't suited.

Quote:

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Originally Posted by mikeyakame

...but I've found a quad core running at 3.4-3.6ghz is much faster for compiling, encoding and even simultaneous drive defragmenting than a dual core even running at > 4.5GHz could ever be.

In other words if you don't need the full use of a quad core, you will probably see more benefits from a higher clocked dual core. It has nothing really to do with gtl or anything else, the VRM on the MF/RF struggles at 500MHz FSB for a quad core, so if 500Mhz FSB and up is your goal then either of those boards aren't suited.

---

The 1st quoted sentence seems to be totally the opposite of the next sentence?

(I have no experience with Intel duals -- went from an aging abused AMD 4800 to the quad in my sig. Just looking to see if I made the right choice).

right now i am trying to get e8600 over 5ghz with rampage formula. duals over 5ghz beat quads at 4ghz in most apps except maybe encoding and like stuff. its 25% higher clock rate

asus x38/x48 are not capable to adjust gtl independently on each core pair.

Quote:

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Originally Posted by davidk21770

The 1st quoted sentence seems to be totally the opposite of the next sentence?

(I have no experience with Intel duals -- went from an aging abused AMD 4800 to the quad in my sig. Just looking to see if I made the right choice).

---

How so? I read over it again and it sounds right to me! For those who don't need to thrash the CPU for intensive tasks a quad core might not make that much sense. I personally find it does.

Quote:

---

Originally Posted by dionysio

right now i am trying to get e8600 over 5ghz with rampage formula. duals over 5ghz beat quads at 4ghz in most apps except maybe encoding and like stuff. its 25% higher clock rate

asus x38/x48 are not capable to adjust gtl independently on each core pair.

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\Those clocks are too high to ensure data validity for anything extremely intensive. Clocks mean nothing if you cant ensure valid data which is critical for certain tasks.

And yep, no individual address / data gtl reference voltage adjustment for either die on the x38/x48 bios' which is kind of a let down.

Quote:

---

Originally Posted by davidk21770

The 1st quoted sentence seems to be totally the opposite of the next sentence?

(I have no experience with Intel duals -- went from an aging abused AMD 4800 to the quad in my sig. Just looking to see if I made the right choice).

---

Nah, I think it's not the opposite because Mike stats that when you don't use the quad to its full potential a dual will be faster. Meaning if you don't use it for encoding and stuff you would be fine with a dual core CPU. At least that's how I interpreted it.

I'm certain that is what he meant. For multithreaded programs that take advantage of all 4 cores of a quad, a moderately clocked quad will be better than a dual core, but for applications that do not fully utilize all 4 cores, a faster dual core cpu would be better.

can anyone provide a guide for DFI P35 UT GTL reference guide for 63-61% reference... i found its different from other board...

currently running 61-61-61 for my e8400 can it works fine... but still curious to know wat percent of reference i am in for vtt of 1.2v as i tweak the current values with trial and errors.... which takes lotsa time.

Been Googled around for a long time, only found those 67% references tables and explaination...

for e8xxx series gtl is 50 -55% of vtt

very nice OP and great responses, big thanks to mikey for layman's explanation. Ive learned alot more here, than with the ultra technical explanations on techrepository and anandtech.

Quote:

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Originally Posted by Pisklink

Nah, I think it's not the opposite because Mike stats that when you don't use the quad to its full potential a dual will be faster. Meaning if you don't use it for encoding and stuff you would be fine with a dual core CPU. At least that's how I interpreted it.

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It just didn't hit me that way... The way that you and mikeyakame are interpreting it, it makes sense.

i am currently running my X38 P5E with the maximus formula 1207 bios

i run my Q9650 at 3.6 ghz (9x400)at 1.20v(1.18v in everest). vNB 1.33v, NBGTL 67x, CPUGTL 63x, DDR2 2.1v. pretty sure vFSB is 1.2v.
i will check my other settings when i get home, maybe i can find alot more speed from this setup...

whats the max safe voltages for CPUPLL and VFSB? from what i read on this thread CPUGTL Voltage should not exceed 1.0v for a 45nm Quad (calculate and adjust CPUGTL so not to exceed this)and a vFSB should be about the same as cpu Vcore. correct?

anyone know what the max NBGTL voltage is for the X38?

its relative to vNB. Higher GTLREF voltage = higher likelyhood of noise in signal. CPUPLL should generally be about 0.3-0.4v higher than vCC. vTT depends on what vCC and vNB are. Safe limit of vTT would probably be around 115-120% of vCC. Safe limit of CPUPLL, just make sure the differential between vCPU_PLL and vCC are not larger than 0.3-0.4v. Keep vCPU_PLL under 1.7-1.8v if you are concerned.

Quote:

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Originally Posted by aka_titan

i am currently running my X38 P5E with the maximus formula 1207 bios

i run my Q9650 at 3.6 ghz (9x400)at 1.20v(1.18v in everest). vNB 1.33v, NBGTL 67x, CPUGTL 63x, DDR2 2.1v. pretty sure vFSB is 1.2v.
i will check my other settings when i get home, maybe i can find alot more speed from this setup...

whats the max safe voltages for CPUPLL and VFSB? from what i read on this thread CPUGTL Voltage should not exceed 1.0v for a 45nm Quad (calculate and adjust CPUGTL so not to exceed this)and a vFSB should be about the same as cpu Vcore. correct?

anyone know what the max NBGTL voltage is for the X38?

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above is true, vCpu_PLL is at 1.5v the lowest available setting. thing is i cannot get this cpu to post at any higher, no matter what voltages i throw at it.. i don't understand such good overclocks with such low volts..it even passes OCCT...My Q6600 Run 3.6ghz and 450mhz FSB on this board...

Quote:

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Originally Posted by globi-wan

for e8xxx series gtl is 50 -55% of vtt

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Wow. There are so many conflicting opinions on this GTL stuff it's astounding. One guy says "don't go anywhere near that value", then someone else says something completely different.

Now we learn that GTL for E8xx series is 50-55%, yet an Asus board, which has two different values, sets it to 0.63% and 0.67%.

It's no wonder just about everyone is clueless, including me. I know nothing more than I did before this thread was started.

:confused:

Quote:

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Originally Posted by Dee

Wow. There are so many conflicting opinions on this GTL stuff it's astounding. One guy says "don't go anywhere near that value", then someone else says something completely different.

Now we learn that GTL for E8xx series is 50-55%, yet an Asus board, which has two different values, sets it to 0.63% and 0.67%.

It's no wonder just about everyone is clueless, including me. I know nothing more than I did before this thread was started.

:confused:

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Why, just because one user says it's 50-55% , but hasn't elaborate on this or gave some source information?
NOFI, but the guy only posted 4 times and his join date is of april this year. So I for one am sticking with the info Mikeyakame is giving us on this issue

I see your point, although I don't think the amount of time a user has been registered should mean all that much.

Looking at my join date you'd assume I was a n00b here, well this isn't so. It's my second account, I've actually been here since 2005, but I kinda expect the members here to see me as a n00b to overclocking, hardware, and forums in general. I'm only new to overclocking Intel systems. AMD was my brand for the last 4 years, and now things are all different!

And it does get slightly confusing.

Anyways... back to the point. I'm just so tired of the fluctuation in opinion and never knowing who is right or wrong. I don't just mean in this thread, but all over the Internet. There is no solid info anywhere as to which values are correct, how much voltage (be it vTT, PLL, vNB, etc) is "safe", and how to set it all up correctly. Not that I don't trust Mike's posts, on the contrary, he seems a very knowledgeable guy. I'd like to follow the advice here but the things I've tried so far have gotten me nowhere, which then makes me look further into it, only to discover about a million different opinions!

I have to laugh, though. :D Especially as you value Mike's opinions, yet he's been here only since May 2008! ;)

This thread is exactly what I've been looking for. Never really understood these GTL ref values, so maybe with this information, I can get my Q9450 stable above 3.6.

Quote:

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Originally Posted by Dee

I see your point, although I don't think the amount of time a user has been registered should mean all that much.

Looking at my join date you'd assume I was a n00b here, well this isn't so. It's my second account, I've actually been here since 2005, but I kinda expect the members here to see me as a n00b to overclocking, hardware, and forums in general. I'm only new to overclocking Intel systems. AMD was my brand for the last 4 years, and now things are all different!

And it does get slightly confusing.

Anyways... back to the point. I'm just so tired of the fluctuation in opinion and never knowing who is right or wrong. I don't just mean in this thread, but all over the Internet. There is no solid info anywhere as to which values are correct, how much voltage (be it vTT, PLL, vNB, etc) is "safe", and how to set it all up correctly. Not that I don't trust Mike's posts, on the contrary, he seems a very knowledgeable guy. I'd like to follow the advice here but the things I've tried so far have gotten me nowhere, which then makes me look further into it, only to discover about a million different opinions!

I have to laugh, though. :D Especially as you value Mike's opinions, yet he's been here only since May 2008! ;)

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I don't ever tell you to believe me. I'm just trying to help out. AGTL+ is AGTL+, GTL Reference multipliers are the same for all systems and all chips, why...because they all use the same design FSB. That is the reason Asus uses those values for all chips. Intel specifies between 0.65 - 0.69 multiplier, but that doesnt mean you cant deviate under or over if it works better with that particular board. I don't quote anything off forums, all that I know come from tech docs, books and real world applications. Take everything you read online with a grain of salt and form your own understanding based on common sense.

Opinion is opinion, not everything works for everybody depends on where the problems lie. Figuring out that bit is one thing nobody on the internet or even in person can automatically tell you. When I look at a system It takes me playing around to figure out where the weaknesses are, then figure out what to do from there. It's how you need to approach things. It's kinda like changing GTL Reference voltage when the problem lies in the PSU struggling to supply constant voltage, it won't fix the problem no matter how much knowledge you throw into it because the PSU is still the key weakness and without changing it all the knowledge in the world won't get you any further in your process!

I do all I can to help, I'm a pretty busy guy between work and other real life commitments I don't even find much time to work on my own system! Kinda sucks but thats life you know.

Quote:

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Originally Posted by Dee

I see your point, although I don't think the amount of time a user has been registered should mean all that much.

....

I have to laugh, though. :D Especially as you value Mike's opinions, yet he's been here only since May 2008! ;)

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Hmm I see your point. I admit, user time does not say much.

Nevertheless, I'm not running blind on one simple post that says it's 50- 55% which has not been backup by some fundamental info, something Mikeyakame had done numerous times.
For all we it's an assumption because mobo builders are setting vTT to 1.10v now for the 45nm processors. But another reason could be they do this so users don't set it too high like 65nm processors.

I'm following the info Mikeyakame is giving us. And so far is has helped me a lot. Before this topic I could not do 9x500 regardless of what voltage I set for vCC vTT and vNB. After reading this whole thread, writing down his posts with formula's and info about the ideal range for those voltages, I gave it another shot.
Guess what? i'm running stable now. Innitially I set GTL to 63/63/58 because a lot of people with a P45 T2RS plus use that setting for 500MHz and it also corresponds to setting GTL Ref to 55% of vTT.
Afer redoing the math following the guidelines of Mikeyakame (set GTL to 67% of vTT and close to 0.80v) I concluded that GTL had to be set around 67/65/58 or 67/66/58 for my vCC and vTT. After this change Orthos has been running for 4 hours straight, where it would fail after 10 minutes.

Btw, I don't see you as noob :)

I have a theory which may be likely where vTT is partially set based on the chipset. For example the 975 express chipset uses a base vTT of 1.30v probably due to being build on 130nm? node, the p35/x38/x48 are built on 90nm node and use vTT of 1.20v, while the p45 is built on 65nm node and uses a vTT of 1.10v iirc. This may explain certain uses of different gtl reference multiplier by mobo manufactuers to accomodate different process node sized chips on a wider scale. Who knows really, you'd have to ask Asus, DFI, Gigabyte, etcs bios engineers for the exact reason cause I for one sure don't have a credible answer there.

One thing I can be certain of though is that an applicable vTT for the chip is selected via the preassigned VID bits for the processor when running in Auto voltage at default clocks. VID sets vCC and vTT through its bit mask based on its original binning criteria, if you check Intel processor spec sheets you will find this information lies there.

Those 2 statements may seem to negate each other, but perhaps they are simply parts of a selection criteria for applicable final vTT through the bios code.

I was wondering now we're on the subject of voltages and stuff :P In my bios I also have control over the "Clockgen Voltage" which defaults to 3.45v and maxes at 3.75v.

Earlier in this topic you talked about vNB better not be the same as vCU PLL, that's it better to have a gap between the two.
In my bios it's called SB Core/CPU PLL Voltage. So is it safe to say that the Northbrige and Southbridge voltage should not be the same.

And how does one start with tuning CPU and NB skew? Is it derived from the CPU bus speed for example?

Any insights would be very much appreciated.

I think the orginal poster should just say start here with 45nm and start here with 65nm because I read all the technical stuff and just don't care any more. I just want to know where to start with my Q6600...

truehighroller:

If you want to get somewhere, get to know what you are dealing with. There is no success without knowledge....be a real overclocker or leave it be. How do you want to draw your own conclusions if you don't want to know about what's going on on the lowest level while doing low level changes in the BIOS!?

...blind people talking about colors. :shakes:

Mikeyakame:

I can tell from what you posted that you know your technology. I have had an electronics education myself and I have my devices here like DMM and a solder station of the more expensive kind, but so far I had no ways of taking a look at the in-depth specifications of Intel CPUs. My instinct led me to the following settings:

Q9300 C1/M1 on a ASUS P5Q3 Del. board (P45 based)

FSB: 460, CPU: 3450
VTT: 1.36V
VCore: 1.32V
GTL ref 0/2: 0.69x
GTL ref 1/3: 0.67x
CPU PLL: 1.58V
NB Volt: 1.28V

This puts my GTL references perfectly in the 0.8-1V range. 0.69x1.36V=0.9384V. Tho I wonder if I should try to get closer to 0.90 to have a safety margin.

During my testing phase of this new setup I had some latent instabilities that showed me how well towards stability I was when I was changing the GTL references by giving me more or less frequent calculation errors in Prime 95. This only resolved completely by putting the PCIe frequency from 100 to 101! 101 MHz gives me a way greater range of stable settings.

I've had a lot of hassle with this board, partially due to stupid memory timing defaults that ASUS seems to have taken STRAIGHT from the DDR2 versions of this board.

I seem to be hitting a FSB wall now at a bit above FSB 460.

Is there a way to circumvent it? I have had cases where I could boot the system at 480, but even more should be possible for my chip.

That's it for now.

Keep rolling folks, this is one of the most competent threads I've seen here!

:up:

Quote:

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Originally Posted by Amurtigress

truehighroller:

If you want to get somewhere, get to know what you are dealing with. There is no success without knowledge....be a real overclocker or leave it be. How do you want to draw your own conclusions if you don't want to know about what's going on on the lowest level while doing low level changes in the BIOS!?

...blind people talking about colors. :shakes:

:up:

---

Don't talk down to me. I know alot about overclocking. I want a starting point referenced idiot.

Quote:

---

Originally Posted by Amurtigress

truehighroller:

If you want to get somewhere, get to know what you are dealing with. There is no success without knowledge....be a real overclocker or leave it be. How do you want to draw your own conclusions if you don't want to know about what's going on on the lowest level while doing low level changes in the BIOS!?

...blind people talking about colors. :shakes:

Mikeyakame:

I can tell from what you posted that you know your technology. I have had an electronics education myself and I have my devices here like DMM and a solder station of the more expensive kind, but so far I had no ways of taking a look at the in-depth specifications of Intel CPUs. My instinct led me to the following settings:

Q9300 C1/M1 on a ASUS P5Q3 Del. board (P45 based)

FSB: 460, CPU: 3450
VTT: 1.36V
VCore: 1.32V
GTL ref 0/2: 0.69x
GTL ref 1/3: 0.67x
CPU PLL: 1.58V
NB Volt: 1.28V

This puts my GTL references perfectly in the 0.8-1V range. 0.69x1.36V=0.9384V. Tho I wonder if I should try to get closer to 0.90 to have a safety margin.

During my testing phase of this new setup I had some latent instabilities that showed me how well towards stability I was when I was changing the GTL references by giving me more or less frequent calculation errors in Prime 95. This only resolved completely by putting the PCIe frequency from 100 to 101! 101 MHz gives me a way greater range of stable settings.

I've had a lot of hassle with this board, partially due to stupid memory timing defaults that ASUS seems to have taken STRAIGHT from the DDR2 versions of this board.

I seem to be hitting a FSB wall now at a bit above FSB 460.

Is there a way to circumvent it? I have had cases where I could boot the system at 480, but even more should be possible for my chip.

That's it for now.

Keep rolling folks, this is one of the most competent threads I've seen here!

:up:

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Thanks for the support!

Good to see there's still some people out there who want to know how things work to make things work! It's the fundamental I practice. If I don't understand something in particular I go to extended lengths to figure it out so at the end I can make my life easier and find answers to my questions, so I can pose more!
I have somewhat of an electrical background, my fathers an Electrical Engineer and I just enjoy electronics and mechanics of things! So I suppose I spend a lot of time doing all fun kinds of things from working on cars to working on computers and gizmos!

Now with your question. From my understanding the hole at 455-475ish requires a lot of GTL reference voltage to overcome the extremely small area under the curve that exists at nominal voltage. Your method of fine tuning GTL Ref voltage via Prime95 is spot on, and honestly thats exactly how I do it too. Adjust the multiplier based on calculation error frequency. The later the calculation error occurs the closer to ball park the GTL Reference voltages / multipliers is to nominal for that FSB and CPU frequency.

I've played with a DDR2 P5Q deluxe and it wasn't fun and games, it was one of the most unpredictable and poorly behaved chipsets I've encountered (p45 I mean), but it's by no means not without possibility of being tamed. Just really really irritating for the most part. I'd hate to be dealing with the DDR3 version, but its not so much Asus' fault (except for the horrible memory support) but rather Intel being stuck writing bios code to support speeds way above design specs due to user demand.

At 450MHz on the P5Q I know I was using 0/2 = 0.73x, and 1/3 = 0.715x for a 65nm chip with around 1.34v vTT, might have been 1.36v but its been a while. Perhaps try starting around there and see how that goes, I know this seems quite high but the idea is to move the crossing point where the rising and falling edges of bclk0 and bclk1 meet way above where they nominally should be, to a region where a valid logical 1 can be determined.

It would raise the value of vIH (input high), also raising vOH(output high), and since vIL(input low) and vOL(output low) can exist anywhere from 0.3v below the crossing threshold to 0v for a logical 0 there is plenty of area to determine the switch to ground for a logical 0. Raising vIH on the other hand means from my understanding that since ringback will always occur and at the point of the FSB hole you can shift the ringback margin inside the crossing threshold where it won't interfere in determining a valid logical 1. The excessive ringback occurs due to the amplitude of the voltage? required for those base clock frequencies from what I understand. I still have some gaps but I guess I try and do my best to explain it so it makes sense! Hell even I get confused explaining electrical theory sometimes! It's brain racking!

Any questions just shoot and feel free to drop ideas, theories and knowledge we can use to correlate all the data! The more gaps we fill the better we can get the understanding across to more people!

Thanks again for the kind words!

Edit: I also find PCIE freq of around 101-103mhz or 110-114mhz to work better at above 400FSB too. Not sure why exactly but its possible it's something to do with the way the frequency is divided from the base clock and multiplied from the analog PLL clock generator.

Quote:

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Originally Posted by truehighroller

Don't talk down to me. I know alot about overclocking. I want a starting point referenced idiot.

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Whats with the poor attitude mate. You don't come in here demanding and throwing your arms around. Very poor form for such a "knowledged overclocker". Some of us started with no knowledge available and had to figure it all out on our own, and then share it with others to make it easier for them. Then some just expect it to all be available to them with little to no effort while maintaining zero gratitude or manors. It's just really poor form and I'm not talking you down, I'm simply telling you how it is.

Starting point is 0.667x multiplier. If you'd bothered to take the time to read what myself and others have been discussing you would have figured this out. Yeah forums are a mess but that's their nature.

Quote:

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Originally Posted by Amurtigress

truehighroller:

If you want to get somewhere, get to know what you are dealing with. There is no success without knowledge....be a real overclocker or leave it be. How do you want to draw your own conclusions if you don't want to know about what's going on on the lowest level while doing low level changes in the BIOS!?

...blind people talking about colors. :shakes:

:up:

---

That is the poor attitude buddy.

I think it's just a misunderstanding in general. It's better to both leave it at that. This being a technical thread there shouldn't be flaming on anybody's part, after all we just want to share knowledge and help each other, flaming and name calling doesn't fit the bill no matter how you look at it aye. This is one of those areas there isn't always a base value besides what the data we have tells us. From there it's all trial and error and learning. I've also discussed in many posts the ball park settings I use with my Q6600, that is why it's good to read even if you don't care cause the thing is I do care and took the time to post the settings I use even if they are annoying from your stance to find amongst all the clutter.

I just thought it would be good idea to post a good starting point. I have helped alot of people by sharing my settings that I use and just fealt this is what this thread is about and starter settings might be good idea that's all. I agree to drop it as well.

As I said in the first post, most people start with 0.667x Vtt for 65nm and 0.635x Vtt for 45nm, however intel state use 0.667x for both processes, so I'd simply advise anyone to start with 0.667x, and work from there. Some have found lowering it to work best, others need to raise it.

As Mikey said, try to aim for around 0.80v, so that means as you raise/lower Vtt, you must adjust the GTL Ref multiplier to maintain the desired target voltage. If you have a BIOS that has the fixed multiplier and the Y value, use the formula and add or subtract the appropriate Y value to give the desired output voltage.

EDIT - I also use the Orthos calculation error frequency to tune GTL Refs, it seems to be the best way of doing it.