I have got a fairly custom setup - whereby the APU2 board is powered by an ATX PSU, that also supplies power to 4 SATA drives with some custom circuitry to poweron the ATX PSU.
Question is - to shutoff the ATX PSU sensibly I need a pin somewhere from the APU2 board that goes to 0V when the system does a sane shutdown (i.e. OS shutdown and power off, and the power LED goes off) - but there is still 12V Supplied to the board with J18.
This "pin" - or output will be used by me in my custom circuitry to control the ATX PSU shutdown which will remove the 12V from J18 (and the 4 disks)
Ideally this would be something like a 5V whilst powered on and 0V when powered off ( with 12V still supplied to board ) - I *MIGHT* be able to make 3.3v work, but definitely not ideal.