Xbox 360 tech powers backwards compatibility on PC, original Xbox games use Xefu emulation

Microsoft is bringing classic Xbox games to PC for the first time through backwards compatibility, but the technology isn't actually new.

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To prepare for its new Project Helix console, Microsoft is taking a more universal approach to game access, aiming to create a kind of convergence of console generations and software. Original Xbox games are coming to PC for the first time via a new backwards compatibility initiative that seems well-timed to coincide with Positron, Microsoft's rumored disc-to-digital conversion program.

To pull off BC on PC, Microsoft is using old tech. The Xbox app uses the Xenon Fusion (aka XeFu) emulator that was first implemented in the Xbox 360. Interestingly enough, Windows PCs will load up an Xbox 360 environment first, and then run XeFu to emulate the original 2001 Xbox. There's basically an Xbox inception going on here as layers of emulation are taking place.

The discovery was found by Twitter user TheLunarixis, who says:

"Fun fact: The new OG Xbox Backwards Compatibility layer released by Microsoft for the PC is actually an Xbox 360 emulator running Xefu (the OG Xbox emu for the 360), confirmed by the XEX2/STFS magic and strings in the kernel such as 'XENON KERNEL EXITING'. Crazy."

This also implies that Xbox 360 games could come to BC on PC at some point, but nothing has been confirmed.

Frequently Asked Questions

TweakBot answers common questions about this news using TweakTown's own coverage from this page and related content from our archive. Tap a question to reveal the answer, or type your own below.

Question #1

Which emulator does Microsoft use to run original Xbox games on Windows PCs?

Microsoft uses the Xenon Fusion emulator, also called XeFu, to run original Xbox games on Windows PCs. The Xbox app first loads an Xbox 360 environment and then runs XeFu to emulate the original 2001 Xbox.

Answered

Question #2

Does the article confirm that Windows loads an Xbox 360 environment before running original Xbox games?

Yes. The article states that Windows PCs will load an Xbox 360 environment first and then run the Xenon Fusion (XeFu) emulator to emulate the original 2001 Xbox, describing it as an "Xbox inception" of layered emulation. This finding is supported by a discovery noting XEX2/STFS traces and kernel strings such as "XENON KERNEL EXITING."

Answered

Question #3

What evidence in the article supports the claim that the PC backwards compatibility layer uses Xbox 360-era code?

The article states Microsoft’s Xbox app uses the Xenon Fusion, aka XeFu, emulator that was first implemented in the Xbox 360, and that Windows PCs load an Xbox 360 environment before running XeFu to emulate the original Xbox. It cites a discovery by Twitter user TheLunarixis who found XEX2/STFS signatures and kernel strings such as "XENON KERNEL EXITING" as confirmation of the 360-era code being used.

Answered

Question #4

Could this PC backwards compatibility approach allow Xbox 360 games to be brought to PC in future?

Yes. The article states that because Windows loads an Xbox 360 environment first and then runs XeFu to emulate the original Xbox, this approach implies Xbox 360 games could come to backwards compatibility on PC at some point. However, the article also makes clear that nothing has been officially confirmed.

Answered

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"This marks the beginning of a broader effort to preserve XBOX games from the past and bring them to PC over time. And we are not just enabling you to play them on PC. We are also adding new features to make your gaming experience better than ever," reads the announcement on the Xbox Wire.