Thus, is the exact, bit-for-bit copy of the final US PlayStation's core operating system extracted from a mask ROM chip.
While many PS2 BIOS versions exist, the v18 (2.30) from the 90001 model is often sought after for its modernity and stability
Here is a short story about the final days of that hardware.
This is the most crucial aspect of this BIOS. Sony updated the boot ROM on these machines (roughly Q3 2009 onwards) to specifically break compatibility with Free McBoot (FMCB) , the popular softmod that allows homebrew software.
The file string you provided, SCPH-90001-BIOS-V18-USA-230.ROM0
: BIOS v2.30 is famous for patching the "Free McBoot" (FMCB) memory card exploit. Consoles with this BIOS version generally cannot boot FMCB unless they have a specific date code (usually or earlier).