Acer Altos G900 User Manual page 32

16 1 System tour
The figure below identifies the jumper blocks and pin numbers. The
function of each pair of pins is described in the sections that follow.
Figure 8 - Mainboard jumpers
Boot block jumpers
The boot block jumpers are used when updating the BIOS or BMC
firmware in the unusual event that the boot block area needs to be
updated. These jumpers are not used for routine firmware updates.
Use the boot block jumpers only when the instructions with a firmware
update specifically say to do so. When you do need to enable either of
these features, use one of the spares from JP4 pins 1 and 2 or JP25 pins
7 and 8. The table below identifies the function of each pin pair on
JP3.