Microsoft's recent release of original Xbox backward-compatible games for PC utilizes a complex emulation architecture that involves an Xbox 360 emulator running an original Xbox emulator. This "emulator turducken," as it's been described, has already been exploited by independent developers to run other Xbox 360 and original Xbox games on PC, often with varying degrees of success.
The system's underlying technology is a port of Microsoft's in-house Xbox 360 emulator for PC, which then runs XeFu, the original Xbox emulator previously used for backward compatibility on the Xbox 360. This approach mirrors how the Xbox 360 itself handled original Xbox backward compatibility, a method that has also informed emulation efforts on Xbox Series consoles. Developers have identified components like XeO3 (the PC port of the original Xbox emulator) and XWine1 (an Xbox One translation layer) as key to this setup.
This revelation comes from independent developers and technical explanations shared on social media platforms. One developer noted that the PC backward compatibility layer is effectively an Xbox 360 emulator running XeFu, referencing a dump of the Xeon Fusion Emulator from the Fuzion Frenzy PC re-release as evidence. Another developer highlighted the layered emulation as a "beautiful piece of engineering."
The XWine1 project team has stated that combining their work with the official emulator allows for the execution of other OG Xbox and 360 games, though achieving stable performance remains a challenge. While dedicated emulators like xemu for the original Xbox and Xenia for the Xbox 360 have been in development for some time, this insight into Microsoft's internal emulation methods could offer new avenues for game preservation and improved emulation quality in the future.