He loaded it into his analyzer. A standard BIOS has known structures: the ROM file system, the OSDSYS (the browser menu), the CDVDMAN driver. This one had all that. But between the blocks, in the interstitial gaps where there should have been 0xFF padding, there were patterns.

: Enjoy perfect regional mapping. This feature ensures that North American game saves and memory card data interact with the system exactly as they would on original hardware.

4 MB (typically dumped as a single .bin file). Region Code: NTSC-U/C (North America).

You will need a PS2 memory card configured with FreeMcBoot (FMCB).