You do not need to find or download an external BIOS .bin file to run games. You only need the emulator itself and your game files in .iso or .xex format.
If you are working with the (not 360) emulator xemu , or modding an actual Xbox 360 console to play original Xbox games, requirements change: Xenia Xbox 360 Emulator Setup Guide 2026 Скачать xbox360 bios bin
For the most popular Xbox 360 emulator, , the answer is no . You do not need to find or download an external BIOS