Bka,

Expect the Yorkfields to stabilize under different voltage needs. You might want to try 1.425 for the NB and 25 for FSB Term. I've found those to be stable throughout different vCore and GTL ref combos. As for actual vCore and GTL Ref needs, you're pretty much trailblazing here.

Btw, what's your chip's VID in Core Temp?