How to set Forced SD Boot Mode

With some specific abnormal operations, boot parts of SPI Flash can be corrupted.
In this case, OGA board can't enter a normal boot process even though a proper SD card is inserted,
because boot order priority of SPI Flash is higher than SD card's one.

Using a switch, SW18, you can make OGA to enter a forced SD boot mode regardless of SPI flash status.

To recover the crashed SPI flash, please refer to the following wiki page.