My research and AI’s responses seem inconsistent or unsatisfactory, so I prefer to ask these questions to Xbox players, thanks to anyone who takes the time to respond!
- Are the games actually emulated or are they just downloaded digitally using the disc as a key?
- Does the compatibility transform games significantly or is it a remaster-like optimization?
- Is it possible to use this feature offline therefore not caring about any Microsoft server support cessation?
- Are there significant differences in how backward-compatibility works on Xbox One versus Xbox Series X?
- What are some other aspects of this backwards compatibility feature that are worth mentioning?
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Okay the other person is onto the right path but I think it’s important to understand the underlying reasons for how “backwards compatibility” works on the Xbox.
The 360 used a PowerPC architecture, which at the time was very cost effective at the time. Pretty much most things now use x86, our standard 32-bit and 64-bit CPUs are this architecture. (ARM is another type that we are seeing now).
Now, you cannot run code from one PC architecture to another, even emulated this is a very costly procedure, every call to the CPU, every call has to be translated. Even with emulation this is difficult. (Note how we’re still just now getting 360 emulators).
This is mostly why Microsoft and Sony both said no to backwards compatibility, because there was no simple way to take a disc, pop it in, and play.
So after the massive backlash (which they deserved, but also was understandable their point of view), Microsoft created their backward compatibility program. Essentially what they (or developers, not sure who did it) did, was to literally re-compile each entire game for x86, instead of PowerPC. They would then upload the bits to Microsoft, and that is what you download when playing. The disc you insert is purely for checking that you own it, after that you ignore everything else and download the x86 version which is runnable on your console.
So, it stands that backward compatibility wasn’t feasible, it still isn’t “backward compatible”. They rebuilt everything from the source code to run. A pretty massive effort on Microsoft’s part and the developers just so we could play old games. Hopefully you see too why I don’t blame Sony for not going through all of that, it’s a lot of work.
So to answer your questions:
- Digitally downloaded in x86 with the disc as key
- No, it is a simple recompile, from the original source code
- No, since there is only the PowerPC bits on the disc, there is no way to play the game on a newer x86 cpu without downloading the x86 bits
- They work the same, once compiled for x86 it works for all x86 processors. (Caveats in software engineering of course, but in this case you can assume they are the same)
- Microsoft went through a ton of effort to get this working, and developers each had to pull up old projects, figure out how to build them again, and did all of this for free. I’m all for hating on Microsoft for a myriad of reasons, but this was a project that had very little profit for them but did the community a huge service. They have my thanks, and Sony has my understanding for why they didn’t do it at the time.
No, since there is only the PowerPC bits on the disc, there is no way to play the game on a newer x86 cpu without downloading the x86 bits
Something worth adding here, if you happen to know, would be if the games still work after download & install while offline. Microsoft’s been rather inconsistent with this over the years (which is part of why Xbox One fell behind PS4 at launch).
I believe so? I think? It’s been a long time. The only thing I could see that would prevent it is if they require a check when launching it, but I remember if you had the disc in that was enough for it before.
No, it is a simple recompile, from the original source code
Didn’t they use static recompilation?
The Xbox 360 uses a processor with a different instruction set which means the executable on the disc simply isn’t compatible with the Xbox One and Series X|S. For those, Microsoft have worked with game vendors to convert the executable (from binary, not source) to the other platform: “static recompilation”. The new executable must be downloaded to play the game.
For the Xbox One, the architecture is very similar to the Series X|S so it can mostly just run it like you can run Windows 7 games on Windows 11 with compatibility tweaks applied by the operating system.
Addendum for anyone interested in learning more: Xbox One should upscale games to around 1080p, while Xbox One X, Xbox One Series X/S and PS5 can upscale to 4K. If you have any further technical additions on upscale differences they are appreciated.
