2.9.1.4.2 Dual Bootstrap

To facilitate updates of the bootstrap images on an external NVM, the Dual Bootstrap feature can be enabled and configured in the Boot Configuration Packet for the relevant NVM interface. The Dual Bootstrap feature enables the ROM code to look for a second (secondary) bootstrap, in addition to the first (primary) bootstrap on the same NVM. This feature is based on the bootstrap version indicated in the bootstrap image header.

When Dual Bootstrap is enabled, the ROM code selects which bootstrap to launch according to the version number (see Bootstrap Image Format). The ROM code launches the bootstrap with the highest version number. If the primary and secondary bootstrap versions are identical, the primary one is launched. If the selected bootstrap is not valid, the ROM code tries to load and launch the other one.