Our Resident DEVS have revised the PS3 Bootup procedure, with some more interesting information.
asecure_loader is not at start of the NAND. The first 512KB also is skipped, or actually any 512 block of FF is skipped.
Furthermore, the asecure_loader differs per box, possibly encrypted with a per-box key. Files of course are not in clear, that suggests that at every step an encryption/decryption is done.
The boot loader in IDA does not look microcode for IDL, maybe it's encrypted with cpu key (the IBM secure boot/asecure_loader), that can explain also why a NAND dump can be restored only on the PS3 from which it was taken.
asecure_loader ----> lv0 which start lv1ldr or lv2ldr depending on 0 or other number in NAND FS
lvldr ----> lv1.self ----> cell_ext_area partition NAND, boot compressed linux kernel for example