Question about the 3.3V readings and stability

So, I have a AX860i PSU and I have both 220V and 127V at my house, when Im using the 127V the 3.3V readings oscilates between 3.31V and 3.28V, but when Im using the 220V it looks stable at 3.31V... I have a friend which is a professional overclocker and he said that the 220V would only change the primary circuit behavior of the PSU, offering better energy savings, and only that, but then again, I noticed this difference at the 3.3V here in my PSU when alternating between 220V and 127V... So is this normal? What could it be?

Looking at https://en.wikipedia.org/wiki/ATX you should see the specification is:

 

[table=head]Supply [V]|Tolerance|Range (min. to max.)|Ripple (p. to p. max.)

+5 VDC|±5% (±0.25 V)|+4.75 V to +5.25 V|50 mV

−5 VDC|±10% (±0.50 V)|–4.50 V to –5.50 V|50 mV

+12 VDC|±5% (±0.60 V) |11.40 V to +12.60 V|120 mV

−12 VDC|±10% (±1.20 V)|–10.80 V to –13.20 V|120 mV

+3.3 VDC|±5% (±0.165 V)|+3.135 V to +3.465 V|50 mV

+5 VSB|±5% (±0.25 V)|+4.75 V to +5.25 V|50 mV[/table]

 

so the voltages you are seeing are well within the required range.

 

As to why the supply being 115 or 230 affects this I have no real idea, I suspect it does not and you need to gather more data.

 

How long did you sample for and was the overall system power usage minimum and maximum the same for the two tests?

 

How are you measuring the voltages?

 

Looking at my AX1500i then after 18 hours of sampling the +3.3 volt range is 3.297 to 3.344 with the mains supply range being 233.000 to 248.000.