is 1.9 volts safe for an athy 64?
how high is safe voltage for those?

it's safe enough with decent cooling.
got a 2.86 ghz 3d mark score on 1.68 vcore :)

Hard to say what safe voltage is. One of my P4s' died without warning at 1.8V of continuous use for 6 months; temp was never the issue at below 58C.

well, 1.8 V is high for P4 ...