Aaeon PCM-6890 User Manual page 30

You can use J1 to clear the CMOS data if necessary. To reset the
CMOS data, set J1 to 2-3 closed for just a few seconds, and then
move the jumper back to 1-2 closed.
J1
*default
This jumper is reserved to connect a system temperature thermal
sensor in order to detect the system temperature.
18 PCM-6890 User Manual
Protect*
1
2
3
Clear CMOS
1
2
3