Power good signal - wikipedia Power good signal This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( July 2016 ) The Power Good signal ( power - good ) prevents a computer from attempting to operate on improper voltages and damaging itself by alerting it to improper power supply. Contents 1 ATX Power Good 2 Power Good values 3 References 4 External links ATX power good The ATX specification defines the Power - Good signal as a + 5 - volt ( V ) signal generated in the power supply when it has passed its internal self - tests and the outputs have stabilized. This normally takes between 0.1 and 0.5 seconds after the power supply is switched on. The signal is then sent to the motherboard, where it is received by the processor timer chip that controls the reset line to the processor. The ATX specification requires that the power - good signal ( `` PWR_OK '' ) go high no sooner than 100 ms after the power rails have stabilized, and remain high for 16 ms after loss of AC power, and fall ( to less than 0.4 V ) at least 1 ms before the power rails fall out of specification ( to 95 % of their nominal value ). Cheaper and / or lower quality power supplies do not follow the ATX specification of a separate monitoring circuit ; they instead wire the power good output to one of the 5 V lines. This means the processor will never reset given bad power unless the 5 V line drops low enough to turn off the trigger, which could be too low for proper operation. Power good values Power good value is based on the delay in ms, that a power supply takes to become fully ready. Power good values are often considered abnormal if detected lower than 100ms or higher than 500ms. References Jump up ^ Manufacturer of a power supply tester External links Power Good article on pcguide ATX12V power supply design guide 2.01 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Power_good_signal&oldid=807427979 '' Categories : Computer jargon Hidden categories : Articles needing additional references from July 2016 All articles needing additional references Talk Contents About Wikipedia Čeština Español Français Русский Edit links This page was last edited on 27 October 2017, at 21 : 56. About Wikipedia

Question: what is the purpose of the power good signal
Answer: prevents a computer from attempting to operate on improper voltages and damaging itself by alerting it to improper power supply