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

[CryptiK]

Thank you CryptiK and mikeyakame

But how do I know what the default value for CPU GTL ref are when I calculate, lets say Q6600 on a P45 board and I can set the GTL for all cores.

Are the default (auto) like this on a P45 board

GTL Ref 0 = ,635
GTL Ref 1 = ,667
GTL Ref 2 = ,635
GTL Ref 3 = ,667

And if I want ,667 on all cores I hade to ad (+) some (how much is depended on the VTT value) for 0 and 2 and let the 1 and 3 left at auto so they all are at ,667.

I can say for sure the Maximus II Formula has the GTL Ref options as:

GTL Ref 0 = ,635
GTL Ref 1 = ,667
GTL Ref 2 = ,635
GTL Ref 3 = ,667

But with other boards it may be different, also some boards tie two GTL Refs together (ie: 0/2 & 1/3) so you only have two adjustments possible, not four. In this situation 0/2 usually = 0.635x and 1/3 usually = 0.667x but unless they state what it is in the BIOS or in the manual it's anyone's guess.

EDIT - as Mikey said though there is often adjustments going on behind what you are doing and as such are beyond your control, so don't focus on what they are originally but through trial and error establish what settings give you the best performance and stability.