windows versus bios voltage

[vishal]

i have my opteron at 2.5 ghz on 1.4volts in bios but in abit eq it says it is 1.44 volts and in cpu z it says it is 1.439 going up to 1.466. it seems to fluctuate a lot in cpu-z between those to voltages.

my question what is the real voltage to believe?
my psu is an antec neohe 430

 

[vishal]

well uguru utility says it is 1.43 - 1.45 in bios as well. it doesn't vary with load (like when i use prime95).
the reason i wanto know is i want to know what is safe to oc to.