On most newer ATX motherboards there is a wake on lan option, with a
three pin header which wakes the computer up when there is LAN
activity.  You might look at using that somehow.

Alternately, this IS the piclist, after all.  Hook a 12cxxx up to the +5
always on line from the power supply, and a sensing pin to a drive
connector +5v.  Hook another pin to the power-on connector.

Make a program for it which detects when the power supply is 'off' and
have it wait for a short period of time, and turn the power on.

-Adam

"Paul B. Webster VK2BZC" wrote:
>
> Hello Robert.
>
> >>   I would suspect however it to be an open-collector output.
> > It is.
>
> > And for many motherboards, putting a jumper on the 'pwr sw' pins
> > asserts this signal permanently so you don't have to go about pulling
> > pins out of the power cable. RTM!
>
>   A manual with that amount of detail is in my experience (of the
> cheaper motherboards, by and large :) a bit of a rarity.
>
>   Now the power switch is in fact a toggle, but with no facility AFAIK
> for "repeat", so I daresay in this circumstance the toggle logic sees it
> at (true) power-up and toggles ON, then stays that way.  OK.
>
>   I have/ had (sitting behind me as I speak, went "phut"!) a MB with
> that very behaviour now I come to think of it.  Started when you power
> up, but power switch did not work.
>
>   What is *bad* about it, is that when Windoze powers down the ATX, you
> then have to pull the power plug and put it back in to make the thing
> power up *next time*.
>
>   I think this transaction is worth the list's attention ;-)
> --
>   Cheers,
>         Paul B.