about cpu gtl reference voltages:


think of it more as a signaling threshold rather then actual voltage applied to the CPU. Although the data that is transmitted across the FSB is digital, the signal response isn't completely on and off, there is some transition time between there.

http://www.thetechrepository.com/att...1&d=1169236522

In the figures from the post here, think of Vtt and Vss as on and off. The GTLREF voltage is the line that the signal has to cross before the signal is seen to have changed from on to off or vice versa.

http://www.thetechrepository.com/att...1&d=1169078346

As the speed of the FSB scales, the response to changes from on to off can change, resulting in a need to adjust the point that the signal is seen to change up or down. By doing this, you can place the reference point somewhere that it wont be freaked out by the noise in the signal as it changes.

In summary, you aren't actually adjusting the voltage that is provided to your CPU, you are just tweaking the point that it will see as a change in the signal the FSB is sending it to try and squeeze out a bit more stability at higher FSB speeds.