soft ATX AT .. .


http://www.hardforum.com/archive/ind.../t-778565.html

One thing about AT that ATX addressed was that the power switch was a mechanical power switch actually connected to the power supply itself. Flip the switch, it turns on, it turns off, nothing spectacular, no auto-shut down when you close Windows. This was called "hard" switching as it was a physical toggle. ATX power supplies, however, are turned on by an electric signal from the motherboard, which can also be addressed by software allowing auto shutdowns and startups. For this reason, the power switch is actually connected to the motherboard by the PS_ON you describe. There is no actual "switching", the switch is just a "momentary" switch that isn't toggled, but temporarily bridges those 2 pins when it is pressed, completing the circuit there and telling the mobo to send the signal to the power supply to turn on. After you let go, the switch goes back to its previous state of "not connecting" and not doing anything, hence the term "momentary" switch. Press it again, and it connects the circuit again and the mobo knows to tell the power supply to turn off. What does it tell you that the mobo is able to know to turn the power supply on even though it is off itself? There is only one explanation - it means there is always a small amount of current going through even when the system is off, so it is never really completely off. This is called "soft" power switching because physically, the power supply is constantly on, and you are using a "virtual" power switch that is really only sending electric signals to the motherboard and is not actually turning off power. There is often another switch on the power supply itself that physically turns it off so there is zero current running through the PC (best to do this when you got the case open fellas).

, / "14 PS-ON Green" "15 GND Black" ( AT-) , ?