The ATX standard calls for a +/- 5% tolerance on each rail. By rail, the voltages should be between:
| Power Rail |
Min Voltage
|
+5 VDC |
+4.75 V
|
−5 VDC |
–4.50 V
|
+12 VDC |
+11.40 V
|
| Max Voltage
|
+5.25 V
|
–5.50 V
|
+12.60 V
|
| Power Rail |
Min |
−12 VDC |
–10.8 V
|
+3.3 VDC |
+3.135 V
|
+5 VSB |
+4.75 V
|
| Max |
–13.2 V
|
+3.465 V
|
+5.25 V
|
A voltage reading above or below these would indicate a potential issue with your power supply.
Please see the
ATX power specification for details about your PSU power pin-out.