It is important to note that PS2 BIOS files are copyrighted software owned by Sony Interactive Entertainment. To remain legally compliant, the recommended method is to dump the BIOS from your own physical PS2 console. How to dump your BIOS:

Unlike earlier BIOS versions (which included the original PlayStation CPU for hardware backwards compatibility), the SCPH-90006 BIOS completely removes the MIPS R3000A core. It relies purely on software emulation (POPS) for PS1 games. In the raw BIOS, you can see the "dead" memory addresses where the PS1 BIOS used to live—filled with zeroes.

Because a self-dumped scph90006.bin is guaranteed to be uncorrupted, virus-free, and the exact 4MB size required by PCSX2.

There is a lot of FOMO (Fear Of Missing Out) in emulation. Let’s separate fact from fiction.

The PS2 BIOS is responsible for initializing the console's hardware, providing a layer of abstraction between the operating system and the hardware, and controlling the console's behavior. Over the years, several BIOS versions have been released, each with its own set of features, improvements, and compatibility.

Dumping the BIOS requires a modded PS2 (e.g., using Free McBoot or Funtuna) and a USB drive formatted to FAT32.