Here are some facts i found out about the satnav units FX, NX and MCA. On powron boot they all behave the same.
The first thing happens, after OMAP5948 powerup is that it executes the bootloader directly from NOR Flash. This routine resides in the first sector of the Flash memory, which is also somewhat write-protected in normal operation and can only be changed by an system software update, like it is done with the Servicepack CDs.
The bootloader performs basic system initialization like memory setup, clock setup, pin muxing, Board ID evaluation, MMU configuration etc. It also copies the Nucleus RTOS image from Flash into SDRAM memory. It then jumps to the copied image and system goes on running from there.
You can find a copy of the bootloader on the Servicepack Update CD image in dnl/bin/system/arion/*/bootload.bin