Hey Darkman,
I have begun to write an explaination a few times but they are too complicated. If I had a deep understanding of the whole GTL thing it would be easy for me to relay that to you guys, I am also aprehensive about sharing information that is incorrect or not 100% tested as that would do you no favours.
I'll blabber for a bit and hopefully you can pick something useful out from it!
The GTL's are reference voltages, they are based on a percentage of the main (master) FSB-Termination voltage. In the screen shot above you can see by default the three GTL refs are
0.63x
- Ref0/Processor Data Bus
0.67x
- Ref1/Processor Address Bus
0.63x
- Northbridge Data Bus
Ok just that bit of information is confusing enough, firstly I didn't know a Processor has two Buses? but they do, one for Data and one for Memory addressing. The Data Bus is slower and very sensitive to being set incorrectly, the Address Bus is faster and quite flexible to not being set quite right. So thats the two GTL's for the chip the last is for the Northbridge which I believe is a Data Bus so again its very picky to being set just so.
The Three GTL ref voltages are derived from the Master FSB-Termination voltage, they are in fact a percentage so instead of thinking 0.63x think 63%
Example 1:
FSB Termination Voltage = 1.10v
0.63x
1.10 x 63% =
0.7623v
0.67x
1.10 x 67% =
0.8107v
0.63x
1.10 x 63% =
0.7623v
Example 2
FSB Termination Voltage = 1.10v
0.72x
1.10 x 72% =
0.8712
0.67x
1.10 x 67% =
0.8107v
0.62x
1.10 x 62% =
0.7502
The difference between example 1 & 2 is that the CPU-Data Bus has had its GTL increase from 63% to 72%, this has changed the voltage ref from 0.7623v to 0.8712v . . . also the NB-GTL has been lowered from 63% to 62% which is a decrease from 0.7623v to 0.7502v . . . . hopefully you follow that so far.
The Three GTL refs that we can change (two for CPU, one for NB) relate to their corresponding voltages, so for the CPU thats
vCore and for the Northbridge thats
vNB
On a technical level you have to understand this is all about SIGNALS, there are thousands and thousands of frequencies racing up and down every second and they go higher or lower depending on what they are trying to achieve, seperate GTLs provide a reference to these signals so the system is able to descern what the *** is going on, is that a signal for the CPU-Dta BUs or is that a signal for the CPU-Address Bus, the only way it can tell is by the GTL Refs . . .
The ASUS Motherboards I have used so far are very finely tuned up to 400MHz-FSB, you don't need to know what the **** a GTL ref is but once you start venturing above that Frequency you are entering a *personal* no mans land, depending on your specific motherboard, processor, FSB used, memory frequency used etc etc the GTL's will vary, that is why I cannot give you specific settings as they are based on my personal kit!
As anything changes like FSB or voltages you need to re-tune the GTL refs lol!
It's so technical I am struggling to write a post that makes any sense and something that you can act on, just understand that as you increase FSB it becomes harder and harder to get thousands of *SIGNALS* moving backwards and forwards and not collide with each other . . . . consider this diagram
As you move from the left (266MHz-FSB) to the right (450MHz-FSB) you may be able to tell the margin for error becomes less and less, its like trying to fly three fighter jet through a hoop that is 50 yards wide, then 40 yards wide, then 30 yards wide etc, there will come a point where the precision has to be so great that the slightest deviation will cause a crash, what makes this totally mind bogglling is that this is happening several thousand times a second and in both directions!
I'm gonna stop there as its a beatiful day and I am sitting here getting frustrated because I cannot explain things how I want and I know this is because I haven't got a firm grasp of the technical stuff.
GTL Tweaking is most likely kept a secret by the top overclockers, anyone who attains a 600MHz-FSB certainly has GTL tweaking down to pat or is utterly jammy . . . there is also the option that its so ******* hard to explain to others most dont even bother!
