Discussion about the VTT

[Shodan486]

So? Any thoughts or hints? We all know this is the voltage of the FSB (correct me), but raising it up endangers the cpu as well as stabilizes the overclocking systems...but sometimes it brings more trouble than ease the pain...any thoughts on this?

[linuxguru]

Re: Discussion about the VTT

It's mainly a reference voltage for the I/O buffers/logic in the CPU to decide what is high (binary 1) and low (binary 0) on the signal lines connected to the CPU. It's not directly relevant for CPU overclocking - only Vcore needs to be tweaked for CPU overclocking.

However, if the FSB needs to be overclocked in conjunction with an over-volted Vio, then Vth may need to be slightly adjusted accordingly. There's usually no point in indiscriminately trying to overclock the FSB, because there will be a severe reliability penalty.

[PCBONEZ]

Re: Discussion about the VTT

That is correct.

To word it a little differently.

Digital signals are sequences of "0"s and "1"s by way of a voltage that is above or below a threshold value.
The logic voltage pulses are created from Vtt inside IC chips.
Basically the chip applies or removes Vtt voltage form/to the Logic circuit to make a sequence of "0"s and "1"s.

Lets assume an imaginary Logic circuit just to get the idea across.
Vtt will be +1.0 volts.
In our logic circuit a "0" is 0.0 volts and a "1" is +1.0v [which is Vtt].
With threshold a "0" is really 'less than' +0.1v actual voltage. - Not exactly zero volts.
With threshold a "1" is really 'greater than' +0.9v actual voltage. - Not exactly +1.0v.

If there is excessive noise in Vtt then "1"s and "0"s can be 'read wrong' which is a corrupted signal.
- Lets say there is 120 mV of Ripple in Vtt and the next pulse is supposed to be a zero.
Because of the ripple the next pulse may actually be +0.120v which isn't low enough to change the logic state to a zero if the previous pulse was a "1".
.
Hope that makes sense.
.

[Shodan486]

Re: Discussion about the VTT

Marvelous! Thanks, this helpd me much and actually you solved my problem...On one of my VP6 I reach 1.94v VTT !!!, which is for the AGTL quite much ...I can run it only at default settings, all the goddish options of Overclocking are for nothing... Thanks Bonez, this is one of the best answers of all times. I got