ATX standards specify that power supplies have a +/- 5% maximum variance tolerance on each rail. For each rail, the voltages s hould be in between:

5 VDC

+4.75 V to +5.25 V

−5 VDC

–4.50 V to –5.50 V

+12 VDC

+11.40 V to +12.60 V

−12 VDC

–10.8 V to –13.2 V

+3.3 VDC

+3.135 V to +3.465 V

+5 VSB

+4.75 V to +5.25 V