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Author Topic: GTLREF and FSB VTT Voltage Tweaking  (Read 54317 times)

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AaronTopic starter

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*** This is all done at your own risk. I, any user on this forum, this forum, or MSI will NOT be held responsible for your actions! ***

I'm sure you've heard about GTL reference voltages.

I've decided to write a simple guide (it's not that simple any more... lol) so, people can understand how to tweak these voltages, and get those high FSB &/or CPU clock speeds.  I'll get right down to business...

A quick breakdown of exactly what A/GTL+ [Advanced Gunning Transceiver Logic] does:

Quote from: Intel Q9000 Datasheet
Most processor Front Side Bus signals use Gunning Transceiver Logic (GTL+) signaling technology.  This technology provides improved noise margins and reduced ringing through low voltage swings and controlled edge rates.  Platforms implement a termination voltage level for GTL+ signals defined as VTT.  Because platforms implement separate power planes for each processor (and chipset), separate VCC and VTT supplies are necessary.  This configuration allows for improved noise tolerance as processor frequency increases.  Speed enhancements to data and address busses have caused signal integrity considerations and platform design methods to become even more critical than with previous processor families.

Rather optional: read this article on how the values work: http://www.thetechrepository.com/showthread.php?t=87 |  It's a great explanation and shouldn't require you to do any more research into the matter.  However, if you still don't understand how GTLREF works, and how VTT effects it: Google is your friend.


You can tweak the GTLREF and VTT (AKA FSB VTT voltage/FSB Terminator voltage) via the Cell Menu in the CMOS setup.

There are many different GTLREF voltages.  There are GTLREF values all over mainboards.  The ones we want however, are for each CPU die (only P45 boards have the settings to signal each die (so far?)) or both CPU dies (every board excluding P45), and the ICH/NB.  You could guess the names.  They are pretty obvious, and sometimes named differently on each board, but they all do the same thing, generally speaking.

The P45 boards have quite an edge.  You can sometimes get a flaky core that needs more voltage than the rest. You can fix that problem with the individual die settings.

NOTE: You will NOT find these options present on a budget/low-end board.  Do not ask if it will have the options in a future BIOS release - it won't.


According to Intel's datasheets: the nominal voltages for GTLREF are 2/3 of the VTT voltage.  However, I've found better results from setting ~63% on the CPU [Yorkfield and Kentsfield] and ~67% on the NB [780i, P35 and X48].

You use a simple formula to calculate what each value will be:

Code: [Select]
a * b = c

a = FSB VTT voltage
b = percentage
c = GTLREF setting

For example:

1.37v * 67% = 0.9179v - Note how precise my result is. The more precise you are, the better chance you will have of getting in the correct margin. Vnoise must also be taken into account. It's +/-10%.  However, I doubt noise is this high on high end boards.  Call it +/-3-5% if you have a high end board with a good power phase.

NOTE: If upon tweaking, nothing is improved, you may need to go up/down a few notches.



After further investigation to Intel's datasheets.  There is a maximum the GTLREF should be set to both in an above and below manner.  The minimum and maximum should be:

Min:

Code: [Select]
0.550 * VTT = min

Max:

Code: [Select]
0.725 * VTT = max

[For those of you that are quick minded, that means don't go below 55% or over 72.5%]

These GTLREF voltages are terminated on-die, going TOO HIGH will most likely mean the death of your CPU!  Going TOO LOW is guaranteed instability!



Do not hesitate to tweak these values, but do not go beyond the limits!  They can sometimes give you great results.  On the other hand, they can also make your results worse (yes, worse).  That means you need to tweak the values more.  Please keep that in mind.

Post your results in here - I'd like to see them.

Good luck with your tweaking!

If you have anything to add or change here, don't hesitate to contact me!



A sidenote for P45 users:

Quote
MSI Tech.   11/03/2008   This is decision of our engineers which work directly with Intel.   
End User   11/03/2008   They also recommend you don't go about 1.5 volts on the CPU, but this mobo will do it. Is there a technical reason why the GTL Ref voltage will not to 67%. All technical documents from Intel suggest 72% is the limit.   
MSI Tech.   11/03/2008   No, since this is recommended by Intel.   
End User   11/03/2008   I can not set the GTL Ref voltage to 67%, the highest it will go is 63%. This may be limiting my overclocking on my quad core. It there anyway to change this? Thanks

james1701 contacted me via PM and shared this info with me.  It appears MSI refuses to put the GTLREF voltage over the limit of 63%.
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DJRamses

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #1 on: 24-August-08, 08:35:49 »

very fine!  :agrees:
Finaly a User who speak about GTL´s.

I want to add on:

Some overclocking experiments shows, that CPU´s with Quad Core in a general rule need 1% - 3% (68-70%) more GTL.

And Cpu´s with Dual Cores needs 3 - 4% less GTL. Also 63 - 67%

The NB GTL Reference Voltage should be around 67%.-


But i want to underscore AaronYuri :
all GTL voltage me be agreed!!
Otherwise you have blue screens, or the system wont boot! Demage should be not    excluded!

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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #2 on: 25-August-08, 06:59:47 »

Some overclocking experiments shows, that CPU´s with Quad Core in a general rule need 1% - 3% (68-70%) more GTL.

And Cpu´s with Dual Cores needs 3 - 4% less GTL. Also 63 - 67%

That's why I mentioned Vnoise in the post above. :yes:

1.37v * 67% = 0.9179v - Note how precise my result is. The more precise you are, the better chance you will have of getting in the correct margin. Vnoise must also be taken into account. It's +/-10%. However, I doubt noise is this high on high end boards. Call it +/-3-5% if you have a high end board, with a good power phase.

all GTL voltage me be agreed!!
Otherwise you have blue screens, or the system wont boot! Demage should be not    excluded!

Do you mean all GTLREF voltages on the mainboard must be identical, or...?
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DJRamses

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #3 on: 25-August-08, 14:12:41 »


Quote
Do you mean all GTLREF voltages on the mainboard must be identical, or...?


I mean, you should not take a GTL value look like lotto!
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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #4 on: 25-August-08, 14:43:02 »

I mean, you should not take a GTL value look like lotto!

Definitely! :police:
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #5 on: 28-September-08, 07:33:57 »

GTL will be DIFFERENT for the Intel quad cores released up to this point.  That's because they're not NATIVE quad cores.  They're TWO dual cores that are on the same chip but they communicate with each other through the northbridge.

I hope this helps whoever was asking if GTL should all be the same.  :)

It's the whole point of why there is a GTL setting in the first place.  Because even with the best quality control, the two dual cores on a quad processor won't be identical, and when you overclock, those differences get magnified to the point where you need to manually modify the GTL stuff.  If you have a dual core, there's probably no need to mess with the GTL unless you bought a $10 power supply from the back of a van.  :-D

You should explain ringback to everyone Aaron.  :)  Because you have an afternoon to waste right?
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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #6 on: 01-October-08, 21:29:39 »

Because you have an afternoon to waste right?

Hahaha! :lol_anim: Sadly, I have a life to live! ;-)) Google is everyone's friend. Someone else can give the answers, I'm sure.

If you got a crap PSU, you shouldn't be overclocking anyway.

Explaining it in more simpler terms: During the transition from the start to the termination point, there's a period where noise will come into play; this causes a "skew" on the signal. Altering the GTLREF (which atone for the signal's voltage) causes this signal's skew to change. What you're basically trying to find is a "sweet spot" where the transition from start to termination is as clean as possible.

And now we return back to reality! :lol_anim:
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stooper

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #7 on: 05-October-08, 23:11:29 »

Hi AaronYuri and Autumnale,

I'd like to pick your brains if you don't mind.  Both of you have made excellent posts here and on the extremesystems.org forum and have helped me very much with setting up my P7N Diamond.  I've learned a tremendous amount on the finer aspects of CPU OC'ing.

This thread about GTLRef and FSB VTT tweaking is especially valuable.  But would either or both of you care to elaborate more on the relationship between Vcore and VTT?  I've seen references (from both of you and other posters) to http://edgeofstability.com/articles/dfi_p35/gtl/gtl3.html and statements declaring that VTT should not exceed Vcore.  From the link, I've come to understand that Intel processors have a safety mechanism to improve stability, but that raising VTT above Vcore will effectively disable the mechanism.

Code: [Select]
Another issue that most users are unaware of is the relationship between VCORE and VTT. To reduce the amount of ringing at the driver,
Intel has added a weak pull-up device to the output buffer as mentioned above. This device turns on at the beginning of a low-to-high signal
transition, substantially reducing the impedance mismatch between the output buffer and the transmission line. As a result, the amount of
overshoot and ringback is significantly reduced. The source terminal of the pull-up device is connected to the core voltage supply. This causes
the logic high voltage to rise above the GTL termination voltage for one cycle. After one bus cycle, the pull-up device is turned-off and the output
will stabilize at VTT if the output remains in the logic high state. But when we raise VTT above VCORE we have effectively removed the pull-up
device from the circuit.

Therefore can anyone clarify how much of a threshhold exists between VTT and Vcore?  Also, does this rule refer to the absolute minimum Vcore during operation (net of Vdrip and Vdroop under full load), or just the average or max Vcore?

On my P7N Diamond / Q6700 combination, I have VTT (FSB Term Volt) set at 1.293V.  My CPU VID is 1.2625V (per CoreTemp).  With cell menu Vcore set to +0.1250V, my idle Vcore varies between 1.344V and 1.352V as per CPU-Z (~0.04V Vdrip).  At load, Vcore varies between 1.296V and 1.304V as per CPU-Z (~0.05V Vdroop).  The voltages fluctuate frequently but mostly center around 1.352V idle and 1.304V load (Prime 95 Small FFTs).

As such, my Vcore is typically well above my VTT.  But for brief periods, at it's absolute lowest point, my Vcore falls to 1.296V, just 0.003V above my VTT of 1.293V.  Assuming, the readings from CPU-Z are accurate, is this sufficient to not cause any conflicts with the safety mechanism?  I suppose I could lower VTT further but I've managed to run 12 hr+ Prime 95 Small FFTs under the current setup and am ready to FREEZE my cell menu tweaks.

Should I consider my settings stable or continue experimenting with lower VTT (to avoid conflicting with the pull-up safety device)?  In any case (yes, you both do have lives and may not have time to respond), thanks for all your valuable explanations.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #8 on: 06-October-08, 14:29:58 »

Someone of you have problem with GTL on P45 NEO2-F?? I dont have 63-67% VTT Voltage results on CPU GTL REF0 and REF1.

Please help if someone know how to set this.
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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #9 on: 06-October-08, 17:47:12 »

Tygrys, open a separate topic up. This thread is for results not troubleshooting.

Guessing from this statement:

Quote
I dont have 63-67% VTT Voltage results on CPU GTL REF0 and REF1.

You didn't quite understand the post. You must calculate the values yourself, you can't just set a percentage.

Stooper, not sure about the VTT and Vcore relation--I haven't looked into it. It is advised that you keep VTT below the Vcore, however. Judging from that statement it means while it won't effect stock speed stability; it'll definitely hold you back in overclocking.

Like I said with the GTL adjustments: you're looking for that "sweet spot" where the skew is spot on. If you do not achieve that skew, you do not achieve the higher clock speeds.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #10 on: 06-October-08, 21:09:29 »

Stooper, not sure about the VTT and Vcore relation--I haven't looked into it. It is advised that you keep VTT below the Vcore, however. Judging from that statement it means while it won't effect stock speed stability; it'll definitely hold you back in overclocking.

Like I said with the GTL adjustments: you're looking for that "sweet spot" where the skew is spot on. If you do not achieve that skew, you do not achieve the higher clock speeds.

I see.  I think I'm happy with my OC to 3.4GHz.  OCCT, Prime95, and Orthos all seem to be happy too  :-P) Whether or not my VTT is conflicting with the pull-up safety mechanism, the system seems rock solid.  So I'm going to consider the system stable and FREEZE my volt tweaks.  I think I can push OC higher but don't want to raise volts/temps any further.

Thanks again.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #11 on: 07-October-08, 20:58:23 »

i wonder is this some sort of 'safety' mechanism in GreenPowerCenter for P45 platinum boards which prevents the GLTref to be set over 65.5% and NB GLT REF over 62% ?
in BIOS it seems GTLref is limited on 63-64% max
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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #12 on: 07-October-08, 22:49:42 »

i wonder is this some sort of 'safety' mechanism in GreenPowerCenter for P45 platinum boards which prevents the GLTref to be set over 65.5% and NB GLT REF over 62% ?
in BIOS it seems GTLref is limited on 63-64% max

Intel's datasheets state that 72.5% is the maximum.  We don't exactly control how a BIOS is written either.  So the limits are obviously of MSI's own will.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #13 on: 07-October-08, 23:25:59 »

i wonder is this some sort of 'safety' mechanism in GreenPowerCenter for P45 platinum boards which prevents the GLTref to be set over 65.5% and NB GLT REF over 62% ?
in BIOS it seems GTLref is limited on 63-64% max

That's unfortunate that the P45 prevents CPU GTL Ref from exceeding 65.5%.  As mentioned, >67% appears to be very relevant for OC'd quad core processors.  As for the "safety" mechanism I'm referring to, it's unrelated to GTL Ref limits (neither CPU nor NB) in mobo BIOS settings.  Rather, it pertains to VTT considerations for Intel processors...

After reviewing the article on edgeofstability.com, I think I've found the answer to my own question.  When transitioning from low signal (logical 0) to high signal (logical 1), the source voltage is connected to Vcore supply.  This occurs on the leading edge of the state transition, thus aiding to "pull-up" the voltage to high state.  So long as Vcore is higher than VTT, then the signal will be pulled "above and beyond" VTT, in turn helping to reduce overshoot and resulting ringback.  On the next cycle, the signal will settle back down to VTT (if state remains high).  Clearly, this design is only effective if Vcore > VTT.

In contrast, if Vcore is **lower** than VTT, then the "pull-up" mechanism will be insufficient for pulling the signal past VTT voltage level.  This, in and of itself, isn't an issue as the signal will still transition to high state.  However, there will be greater likelihood of overshoot and, in turn, ringback.  Hence, maintaining the VTT < Vcore relationship is an important guideline for improving stability, but it isn't an absolute necessity.  A system may operate very stable despite violating the guideline.  An important factor appears to be the quality of the power supply and amount of noise that occurs.
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AaronTopic starter

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #14 on: 07-October-08, 23:45:29 »

That's unfortunate that the P45 prevents CPU GTL Ref from exceeding 65.5%.  As mentioned, >67% appears to be very relevant for OC'd quad core processors.  As for the "safety" mechanism I'm referring to, it's unrelated to GTL Ref limits (neither CPU nor NB) in mobo BIOS settings.  Rather, it pertains to VTT considerations for Intel processors...

After reviewing the article on edgeofstability.com, I think I've found the answer to my own question.  When transitioning from low signal (logical 0) to high signal (logical 1), the source voltage is connected to Vcore supply.  This occurs on the leading edge of the state transition, thus aiding to "pull-up" the voltage to high state.  So long as Vcore is higher than VTT, then the signal will be pulled "above and beyond" VTT, in turn helping to reduce overshoot and resulting ringback.  On the next cycle, the signal will settle back down to VTT (if state remains high).  Clearly, this design is only effective if Vcore > VTT.

In contrast, if Vcore is **lower** than VTT, then the "pull-up" mechanism will be insufficient for pulling the signal past VTT voltage level.  This, in and of itself, isn't an issue as the signal will still transition to high state.  However, there will be greater likelihood of overshoot and, in turn, ringback.  Hence, maintaining the VTT < Vcore relationship is an important guideline for improving stability, but it isn't an absolute necessity.  A system may operate very stable despite violating the guideline.  An important factor appears to be the quality of the power supply and amount of noise that occurs.

Where's a clapping smiley when you need one?
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #15 on: 08-October-08, 00:37:45 »

Intel's datasheets state that 72.5% is the maximum.  We don't exactly control how a BIOS is written either.  So the limits are obviously of MSI's own will.

well i was bit shocked this same problem exist even in the performance BIOSes and it most likely explains the 'OC walls' these MSI boards have ...
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #16 on: 29-October-08, 10:33:58 »

I partially understand the principles behind GTL referance voltage. Orthos wil run for 2 sec on auto and 20min after I messed around a bit, the thing I don't understand is that my MSI P43 Neo-F has CPU GTL Ref0 and CPU GTL Ref1.
Leaving those settings on auto Ref0 will be 63% of VTT, but Ref1 has a much higer percentage(didn't calculate) of VTT. Where does this difference come from?
Since I have a budget motherbord and a E7300. I should not be able to tweak the individual cores, but what if I can do that, why is there a big difference between ref0 and ref1?

I'm running bios 1.6 and 8.5x415 with 1.36Vcpu and 1.25VTT.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #17 on: 29-October-08, 11:00:58 »

I am not sure of the differences between those two settings because I have no experience with the board.  However, because 0 is 63%, I'm guessing that's for your CPU die, and because the other is a higher percentage [67-69%], it's probably for the ICH.

This being said, take it with a grain of salt, as only MSI could really say what is truly what.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #18 on: 04-November-08, 15:43:13 »

After reading some articles again, I answered part of my own question. Ref0 is for data and Ref1 is for adresses. I have yet to find out if the diff in % of VTT between ref0 en ref1 should be as they are on my board.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #19 on: 04-November-08, 15:54:11 »

Quote
Leaving those settings on auto Ref0 will be 63% of VTT, but Ref1 has a much higer percentage(didn't calculate) of VTT.

Razkin, I am curious about one thing:  How do you know that there is a difference between those values, when they are set to AUTO?  The values do not appear in BIOS as far as I know, so which tool do you use to monitor the AUTO Settings?  If I am not mistaken, Green Power Center does not support your Board and Dual Core Center (at least as far as I remember) does not display GTL Voltage Settings.  I am asking, because when I check the GTL Auto Settings with Green Power Center on my P45 Platinum, the values are always identical:



...always 63.45% of VTT, to be more precise.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #20 on: 04-November-08, 16:10:27 »

It's an option in the Cell Menu. I know the option isn't present in bios v1.2, but it is in v1.6. When it is on auto I just change to the next and previous setting to determine the auto setting in volts. I can see the direct changes tot Ref0 and Ref1 when I change vtt and the result is the same. Ref0 will be about 63% of VTT and Ref1 will be about 66,5% of VTT.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #21 on: 04-November-08, 16:14:41 »

Same here if I do the same thing in BIOS, however, left on AUTO, Green Power Center will show identical values.  What I am trying to point out is, that checking the settings in BIOS and inferring from the setting that comes after AUTO what the AUTO setting looks like, may bring you on the wrong track.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #22 on: 04-November-08, 16:47:48 »

Well it's interesting that GPC shows identical values on auto and that your bios behaves as mine. I have no other tools than bios to check voltages for vtt etc. The bios should be right, but could be wrong. In my experience it's more likely that the program is wrong. Only way to be sure is by using a multimeter. What does GPC show, when you manually adjust Refs?
To be more precise(bios)
Ref0 0.7859 ->auto-> 0.7900
Ref1 0.8262 ->auto-> 0.8300
Vtt: 1.25
Ref0: 62,8% ->auto-> 63.3%
Ref1: 66,1% ->auto-> 66,4%

Ref1 percentage is slightly off, could be my memory, but I also tested with higer/lower vtt, so I could have made a mistake when calculating.
VTT on auto should be 1.2 and one step higer is 1.21 and  one step lower is 1.19. It is not certain until checked with a multimeter but I all does seem to be logical...
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #23 on: 27-April-09, 06:04:53 »

Did anyone ever get any improvements changing gtl ref volts?

Particularly on a dual core.. is GTL ref 0 for data and ref 1 for addresses? What does this mean and what O/C settings would you recommend?
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #24 on: 09-January-11, 17:46:30 »

Hello,

Im new to overclocking and trying to learn this.     SO far my attempts have been failures

Im trying to understand this   ax b= c    formula

How do I know what to make "A" ( my FSB VTT)  ?     I understand how to get C from a and b ,, but how do I know what to set A to?

also It looks like my board has the 2  GTLREF references.  One for each die.  It also has a MCH GTL Reference.

Here is what I have so far:ANy suggestions?    (the FSB is set to 400 and the original was 333) 

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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #25 on: 16-January-11, 08:10:00 »

Sorry noob asking, is there GTL setting in chipset P55?
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #26 on: 16-January-11, 14:52:04 »

Sorry noob asking, is there GTL setting in chipset P55?

Not sure.  As far as I know it's FSB/GTL and QPI/DMI.  Should still be reference voltages options.  Unsure about GTL specifically.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #27 on: 25-September-16, 15:44:59 »

Hello there.

Sorry for digging this out, but I have a few questions regarding this topic.

On my P7N2 Motherboard with an Wolfdale Dualcore I can set the following:
FSB Termination Voltage / VTT between [1.056V and 1.313V]
CPU GTL Reference Voltage  between [0.65-0.666 and 0.668-0.688]  (Factor the VTT gets multiplied with.)
NB GTL Reference Voltage  between [0.591-0.611 and 0.668-0.691]  (Factor the VTT gets multiplied with.)

The Reference Voltages are set in absolute Volts, depending on the VTT and the factor from above.


So far I noticed that there is a relation between NB Voltage and VTT.
The higher the NB Voltage gets, the higher the VTT has to go up in order for a basic amount of "stability". (Boot to Windows and don't freeze on the desktop without load within a few seconds.)

I am trying to get a FSB of 450 MHz stable, NB Voltage is currently on 1.35V.

First I left VTT, CPU GTL and NB GTL on Auto, but with VTT on Auto I didn't manage to get to the Desktop anymore without the system not POSTing or simply freezing somewhere on the way.
So I increased the VTT beginning from the lowest value to make it to the desktop. That would be 1.214V.


Now the questions:

1. How do I know what combination of NB Voltage and VTT is "right"?

I messed with it for hours now, setting the NB Voltage (1.35 i.e.) and increasing the VTT in ~0.05V increments. (It regulary has 0.01-0.02 increments.)
But so far, there hasn't been any value I could get stable trough Prime95 Large (672k) for more than 20 minutes without producing errors.
Even if I go for the "give em all you got" way and set the VTT straight to 1.313V for any NB Voltage (1.35/1.38/1.42/1.47/1.5) it won't last long. It appears that too much VTT leads to instability aswell in form of rounding errors, for 1.5V even freezes.


Then I tried to play around with the GTL Voltages for a few of the "better" VTT values (that went close to 20 minutes) but two things seem strange to me:

2.1. From what I read in OC guides, the CPU GTL should be between 61...68% for Wolfdale Dualcores, depending on where you look. Some say it should be equal to the NB GTL which should be at 67%. And then you can read that the NB GTL should be more important than the CPU GTL, but I couldn't find any specific values for it, apart from the 67%.

The point that gives me headaches are the values that I can set in my bios. As mentioned above, the NB goes from x0.591 to x0.611 (small increments of 0.0005) and from x0.668 to x0.691 (wide increments of 0.002). That would be sufficient for the ~x0.67 but what is the fine scaled area between .591 to .611 for?

The CPU GTL, on the other hand, goes from x0.65 to x0.666 and from x0.668 to x0.688. With the recommendation in mind, everything from 61% to <65% is simply out of range for me.

First I thought I mixed up CPU and NB GTL, but I am pretty sure it's this way and not the other way around.

2.2. Sometimes you read that most people only use the GTLs in order to reduce their CPU and NB Voltages by a notch or two, once they got their system stable. Sometimes you read that the GTLs can make the difference between not POSTing and a stable system.

In order to find the right GTLs, how should someone start?

2.2.1.
My problem:
Since my VTT isn't stable without adjusting GTLs so far, I can only guess what VTT would be a proper base value for testing.
Then I picked one Prime95 Large FFT lenght that caused the fastest errors for me (672k) and let it run, while setting NB and CPU GTL both at once.
Since I have my CPU multiplier on the lowest setting (6x instead of 8x) and the CPU Voltage is sufficient (Prime Small without errors, freezes or BSODs), can I leave the CPU GTL on Auto and purely concentrate on the NB GTL? Or do the interfere with each other and both have to be on spot at the same time?

2.2.2.
The second problem:
I read that you should start with one value x and note how long Prime takes to spill errors / freeze. Then you move in both directions from x (x+y and x-y) and see if the errors / freezes appear faster or slower. With that in mind you see in what direction you have to move and when you get to the right value.
I am not sure if they mean full Prime Large runs with this or not. But I tried it purely with 672k and thought that it would last longer once I get into the right direction.

The problem is, that it appears to be completely random how long this single test runs. If I use the same GTL voltages and let the same test run twice with the same settings, it can happen that it runs for 40 minutes before producing an error in the first run and in the second run it fails after 3 minutes. But if it's completely random within one test and let it run in Prime Large for some amount of time, how would I know if it failed at test #4 and not #3 because it got better and not because I simply got lucky?
In my current understanding, even there I couldn't say for sure if adjusting the GTL +y or -y was good or bad since it could be somewhat random aswell.



I am not sure wether or not there are still people around here that read this and are able to help. I hope there are. Help is appreciated, thank you very much.
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Re: GTLREF and FSB VTT Voltage Tweaking
« Reply #28 on: 26-September-16, 09:06:42 »

This thread is five years old. Please don't resurrect dead old topics. Most people who posted here aren't even active anymore. Please open your own.

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