Sorry to pop in on your thread, but I figured at least 4 people in here would know the answer to my question :)
I just added a Chilly1 single stage to my P4 550 and hit 5GHz (unstable, but I got my screenshot/verification ;). I have not gone over 1.60Vc because I am not really sure what is "safe" on phase. It's a D0 step with default Vc of 1.40V (1.38V?). If anyone can shed some light, I would appreciate it!
Thanks