Scph-90001-bios-v18-usa-230.rom0 -

: This is the recommended legal method. You can use a tool like Launch Elf on a PS2 with a Free McBoot memory card to extract the BIOS directly to a USB drive.

Are you trying to play a Japanese game? The USA BIOS will reject it. You will get the infamous screen despite a valid disc image. You need either a Japan BIOS ( scph9000.bin for NTSC-J) or a region-patched cheat. Scph-90001-bios-v18-usa-230.rom0

– Indicates the BIOS version. Sony updated the PS1 BIOS several times across different motherboard revisions. Early PS1 models (SCPH-1001) used a much older version. Version 18 is one of the last and most refined BIOS revisions for the original PlayStation, found only in the late SCPH-900x series. It includes minor bug fixes, potentially anti-piracy tweaks, and improved CD-ROM drive handling. : This is the recommended legal method

The SCPH-9000x series represented the pinnacle of the original PlayStation hardware design before the PS2’s launch. It integrated the CPU, GPU, and I/O controllers into a single custom LSI chip (the "PM-41" or similar), reducing cost and power consumption. The BIOS on this chip was version 18 (also called "ROM Version 4.5" in some internal Sony documentation). The USA BIOS will reject it