The only 100% legal way to obtain a PS2 BIOS is to .
AetherSX2 does not come with a BIOS file due to legal reasons, as the software is proprietary and copyrighted by Sony. Most BIOS files come in a .bin format. ps2 bios download aether sx2 usa
To play North American games (NTSC-U), you typically need a USA BIOS like SCPH-90001 or similar. The only 100% legal way to obtain a PS2 BIOS is to