BIOS IOP REBOOT - SIF Reboot Server

REBOOT installs a custom SIF command handler for 80000003h and waits for this command to be sent.

IOP Reboot Procedure

The EE sends SIF command 80000003h with an argument of rom0:UDNL [last image file]..[first image file] [-v]. An example image path is cdrom0:\MODULES\IOPRP243.IMG;1 (sent by Atelier Iris: Eternal Mana).
The -v flag is recognized by UDNL but doesn't seem to have any effect.

REBOOT calls MODLOAD.ReBootStart. MODLOAD cleans up all module libaries and jumps to IOPBOOT. IOPBOOT bootstraps SYSMEM and LOADCORE. LOADCORE loads all modules in IOPBTCON2. When MODLOAD is reloaded, it installs a post-boot callback in LOADCORE. This callback jumps to the UDNL module.
UDNL scans all provided image files and finds the newest modules in each of them, then triggers yet another reset by bootstrapping SYSMEM and LOADCORE. LOADCORE reads from IOPBTCONF and loads the newest modules in the image files or the ones in the boot ROM. The reboot is now complete.

Image File Format

Like the BIOS, an image file contains a ROMDIR filesystem. An image file usually contains a RESET file of zero bytes, ROMDIR, EXTINFO, and a list of newer IOP modules to load.

An example of the usage for this IOPRP images is the Sony DVDPlayer Update discs (and FreeMcBoot installer as a homebrew example). they use these IOPRP images to replace the SECRMAN driver with an advanced version that allows binding KELFs to a memory card to install them there as system or DVDPlayer Updates