Microsoft shipped a native Xbox 360 emulator with its new backwards-compatible releases on PC - modders quickly got 360 games running with minor tweaks

The Discovery

Microsoft dropped four OG Xbox titles on PC a couple of days ago, and they came with a native Xbox 360 emulator baked in. These games are packaged as Xbox 360 files, so the emulator runs them as such, then another emulator takes over to translate OG Xbox code inside the virtualized 360 environment.

The discovery was initially made when data miners looked at the package contents of these backwards-compatible titles. Neo Te Aika found out that they were packaged as standard Games on Demand, or GOD files, which is the official file format used by Xbox 360 hardware. A GOD package contains the actual game, its headers, and DRM. By using a GOD extractor, modders were able to open them and convert them into a base ISO that can be played with an emulator, or on a jailbroken Xbox 360.

How It Works: Emulator Within an Emulator

Nathan on X scoured through those same files to find something called Xe03. Also called Fission, Xe03 is Microsoft's official Xbox 360 emulator that comes baked into the Xbox One and Xbox Series consoles for backwards compatibility. Within the Xbox 360 environment, Microsoft already had another emulator called XeFu, or Fusion, that emulates the original Xbox. So, it's basically an emulator within an emulator. That's how modern Xbox consoles have been able to play OG Xbox titles. To Xe03, it's just opening a standard Xbox 360 package, but the binary inside is coded to launch XeFu, which then takes over to run the original Xbox game.

When Microsoft released backwards compatible Xbox games on PC, people expected the company to have built an x86-native OG Xbox emulator from scratch - an emulator that didn't rely on an outer layer or any external components. Instead, what Microsoft did was simply recompile Xe03 to run natively on x86 PCs instead, indirectly handing over the ultimate 360 emulator to the community.

Modders Get 360 Games Running

By modifying the app container and swapping out game packages, projects like XWine1 and independent reverse-engineers bypassed the inner OG Xbox layer (Fusion) and managed to load raw Xbox 360 executables (.xex files) directly into Xe03. The results have been mixed but incredibly promising, nonetheless.

The XWine1 team was able to get the following games to boot and run with varying degrees of stability:

• Plants vs. Zombies
• Steins;Gate
• Fuzion Frenzy
• Midnight Club: Los Angeles

Fuzion Frenzy is actually one of four OG Xbox titles that Microsoft officially released, so that one is particularly well-optimized.

Performance and Optimization

Since the hard part of reverse engineering first-party code has already been done by Microsoft, optimization remains the only challenge. As time goes on, and the specific emulator files are fine-tuned for general usage, we should expect more and more titles to run flawlessly.

Microsoft has also promised to release more official backwards compatible titles on PC, but it hasn't said anything about Xbox 360 games. Therefore, the discovery of Xe03 holds immense potential for the future of Xbox 360 emulation on PC - the community just has to focus on optimization now. This development can be particularly fruitful for handhelds that are power-constrained; Xe03 has very light minimum requirements for devices like the ROG (Xbox) Ally and Lenovo's Legion Go lineup.

Features and Future

Moreover, Microsoft's PC version of Xe03 also upscales the original 480p output of OG Xbox games to 4K. It also adds built-in V-Sync, anisotropic filtering, enhanced anti-aliasing, and borderless windowed modes. Since the games were distributed through the Xbox PC app, they're part of the Xbox Anywhere program, so if you own the digital license of said game on console, you get it for free on PC (and other places). Microsoft will also bring Xbox Achievements support to backwards compatible titles soon. The last two elements will likely be ignored by the modding community since the OG Xbox virtualization is the important part, enabled by the Xe03 engine that has now become the main takeaway from all this.

To be clear, open-source emulators such as Xenia have existed for years and provide a highly-satisfactory Xbox emulation experience, but Microsoft's official, in-house solution should be more efficient.