Hello! Since PS2DEV is down, Is there any good info on how the PS2 BIOS works? o_o I have a slight feeling it's similar to the PSP's kernel.
What do you want to know? The boot ROM (rom0 contains the kernels for both the EE and IOP, and both processors share the same reset vector + bootstrap code (although the bootstrapping code will branch differently, depending on the CPU PRid).
Whenever a website is down or gone for good, remember the Web Archive http://web.archive.org/web/20101020182537/http://ps2dev.org/ (if a page within the website doesn't work, try with previous dates in the archive as it may have been archived in a previous run but not in the one you're looking at)