Emulators became better at "HLE," which involves intercepting BIOS calls and handling them within the emulator's own code, reducing the need for a separate, full BIOS replacement.
Technically, FPS2BIOS was not a full replication of the Sony BIOS’s protected kernel. Instead, it was often a lightweight bootloader designed to initialize the PlayStation 2’s Emotion Engine (EE) and the I/O Processor (IOP) just enough to execute specific programs. In the context of development kits and early emulation testing, FPS2BIOS served as a bridge. It allowed developers to load executables (ELF files) over a network connection (via the PS2’s Ethernet adapter) or via USB, bypassing the standard CDVD boot sequence. fps2bios