ATX Power supply soft power switch hack...Anyone done it?

I am trying to use a ATX computer with amd 900 athalon chip in a
machine and would like to simply power the computer up by switching
the ac line.

This machine has a main power switch on the back of the power supply
which turns off all the power but when switched on, you still have to
use the soft power switch ( a spst momentary push button ) to boot
the machine and to shut it down.

Jumpering this switch does not make it power on when the line is
switched and there are no bios settings which enable this feature
either.

Has anyone else dealt with this problem?

Thanks

Bill