Hi all!
I think, this can be put onto the FAQ.
I found the solution that works for M789 and is very easy and cheap. It also must be a universal solution, helping to power-up any ATX motherboard on power up of the PSU.
Just take a small capacitor (i used a 2uF one) and put it in parallel with the standard power button on your case. Or just connect the capacitor to the PWR BTN header on the motherboard.
This is much easier and cheaper than using any digital solution (with a counter IC or anything). The principle behind my solution is that upon powering up the PSU, the 5VSB line becomes high on the motherboard. That line powers the circuitry needed to react to the power button. Additionally, voltage appears on one of the pins of the PWR BTN header on the mobo (the other pin is ground). So, when there is a capacitor between the pins, it starts charging. That looks like a short circuit to the mobo. It boots up. The capacitor becomes fully charged and it starts looking like an open circuit to the motherboard. The capacitor is never discharged while the mobo is powered and is discharged quickly after the power is removed. Additionally, the functionality of the power button is preserved - you can still push it to turn the PC off.
In other words, the capacitor is equal to "AC Power Loss restart: Always On" setting in the BIOS.
WBR, Alexander mailto:spirit@reactor.ru