When you power on an SCPH-90001:
The v18 BIOS does all this with a 20% smaller code footprint than v1.0, thanks to aggressive compiler optimizations from Sony's in-house team. Scph-90001-bios-v18-usa-230.rom0
The PS1 BIOS is still under copyright by Sony Interactive Entertainment. It is not abandonware. Distributing or downloading BIOS files from the internet is a violation of copyright law in most jurisdictions. When you power on an SCPH-90001:
This refers to the Version 18 of the Basic Input/Output System. The PS1 BIOS is a 512KB ROM chip that handles booting, CD-ROM decoding, and controller input. The v18 BIOS does all this with a
This is the most important and often misunderstood aspect.
If you see a website offering Scph-90001-bios-v18-usa-230.rom0 for download, that distribution is unauthorized.