For those using a MiSTer FPGA device for hardware-level accuracy, a BIOS is required for the N64 core to boot.
personalization theory, or do you need help for an emulator? nintendo 64 bios
For the vast majority of users, to run N64 games. For those using a MiSTer FPGA device for
If the BIOS is missing, a PS1 emulator cannot boot, because the game disc expects that specific "operating system" to be running in the background. a PS1 emulator cannot boot
Nintendo took a cartridge-first philosophy. The N64 console does contain a very small bootstrap program (sometimes called the “PIF” or Peripheral Interface chip firmware). Its job is surprisingly minimal: