Because Xemu is a fork of (which itself is based on QEMU). QEMU’s philosophy is hardware virtualization. To accurately emulate the MCPX logic gates, the developers realized it was exponentially harder to recreate the boot code from scratch (reverse engineering) than it was to simply load the real firmware into the emulated chip.

Enter . Xemu is the leading open-source, low-level emulator for the original Xbox. It aims for accuracy, which means it doesn't just simulate the games; it simulates the hardware itself. And at the very center of that hardware simulation lies a tiny, often misunderstood, but absolutely critical component: the MCPX Boot ROM Image .

certutil -hashfile mcpx_1.0.bin SHA1

You can verify this using a tool like CertUtil (Windows) or shasum (Mac/Linux).