mynick wrote:


thanks for great explanation
so in modern mobos the on switch grounds a pulled up line, straight to
southbridge
(Possibly there is a Schmitt trigger/inverter in between the two)

+5VSB +5VSB
| |
Pullup Pullup
Resistor Resistor
| PS_ON# |
PWR X----+---- Motherboard logic ---- Open -------------------+- ...
Collector (to
GND X----+ Driver ATX +
| supply) |
(Front GMD GND
Panel
Switch)

Using an ohmmeter, between PWR and PS_ON#, doesn't tell you anything.
There is a silicon chip in the way.

Paul