found this:
However, Asus (and other mboard makers that supply mboards to brand name system builders - e.g. HP, Compaq, Dell, Gateway, and most other brand name system builders DO NOT make the mboards themselves) does NOT normally change which pins are for what on that header, or on other headers on the mboard, even if it is an OEM only mboard.
If you want to know which pins are for what on any header on the mboard, if you download and look at the manual for any Asus mboard of a similar age, the pinout assignments are usually identical to those on OEM only mboards.
In this case, look at amboard manual for a socket 478 mboard, although it probably doesn't matter which socket it uses as long as it was made about the same time (or the pinouts may not have changed over time in any case).
and this:
The ATX specification fixed the worst problems of the AT power supply. It took the power switch out of the mains side, so that safety and reliability improved dramatically. It made the power supply switchable from the DC side, so that software shutdown was now possible. This had the side effect of allowing many new switch styles, since the switch no longer had to carry the full current load of the PC, it could be a mini or sub-mini pushbutton, and could be easily located just about anywhere on the case.
So lets look a little closer at how the PC is powered on. The PSU is powered from the mains supply. Some PSUs have their own shutoff switch, which allows interrupting the mains supply for whatever reason. As long as the PSU is powered from the mains, it is also providing your motherboard with a small amount of power from a connector known as the +5VSB (pin 9 of the motherboard connector, connected to a purple wire), or five volt standby. Even though your system is powered down, you are still drawing a small amount of current from this. The circuits that control the power switch are among the things using that power. When you press the power button, you momentarily close a set of contacts. The motherboard circuity reacts to that signal by sending a signal to the PSU. The signal is called the PS_ON# (pin 16 of the motherboard connector, connected to a green wire), and the setting of a LOW voltage (0V) on this connector tells your PSU to deliver full power to your system. Many of you are probably familiar with the trick of “hot-wiring” a PSU by connecting a pin with a black wire to the one with the green wire. In doing this you are forcing 0V on PS_ON#, which starts the power supply. When your computer does this, the circuit holding that pin low is controlled by software, so this is how a soft shutdown works (as well as things like wake-on-modem or wake-on-LAN).
When the PSU is delivering full system power, it’s also required to hold a HIGH (+5V) signal on a connector called PWR_OK (pin 8 of the motherboard connector, connected to a grey wire), which signals to the system that voltages are within tolerances dictated by the specification. These three signals, +5VSB, PS_ON#, and PWR_OK, make up the “housekeeping” connections to your PSU. They allow the management of power by the system, and together solve the problems with the AT spec.