Phil Spencer Explains How Xbox One Backwards Compatibility Works

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Phil Spencer told Giant Bomb on their E3 Day One podcast that the decision to include legacy support was one motivated by ensuring that Xbox 360 owners feel good about making the transition. There are still a lot of people who have large libraries that might not have had a chance to play every single game, so this is now a “safe place to play” as Spencer puts it.



"Millions of people made investments in 360 content," he said. "We thought the right thing to do was to make that content go forward, but we didn't know [how difficult it would be]."


"[Emulation] is hard," admitted Spencer, explaining that the company was dealing with having to harmonise PowerPC architecture with x86.


"The approach that we've taken is to actually emulate the full Xbox 360 hardware layer. So the [operating system] for the 360 is actually running when you run the game,"
Spencer explained.

"If you watch the game's boot you'll see the Xbox 360 boot animation come up. From a performance standpoint it allows [emulation] to work. We're able to get frame by frame performance equivalents."


"[Xbox Live] thinks you're on a 360, so people have been asking 'hey, why are you playing Mass Effect on the 360?,' I was actually playing on the Xbox One."


Spencer continued to explain that, since the Xbox One thinks it's playing a normal game, features such as streaming and screenshots are supported.

"The 360 games think they're running on the 360 OS, which they are. And the 360 OS thinks its running on the hardware, which it's not, it's running on an emulated VM. On the other side, the Xbox One thinks it's a game. That's why things like streaming, game DVR, and screenshots all work, because it thinks there's just one big game called 360."


Delving deeper, Spencer explained exactly how the emulator packages the Xbox 360 games, and how it compares to Xbox 360's emulation of original Xbox games.

"You download a kind of manifest of wrapper for the 360 game, so we can say 'hey, this is actually Banjo, or this is Mass Effect. The emulator runs exactly the same for all the games.


"I was around when we did the original Xbox [backwards compatibility] for Xbox 360 where we had a shim for every game and it just didn't scale very well. This is actually the same emulator running for all of the games. Different games do different things, as we're rolling them out we'll say 'oh maybe we have to tweak the emulator.' But in the end, the emulator is emulating the 360, so it's for everybody."


Asked about whether Microsoft would require permission from game publishers to adjust game code, Spencer clarified it would not be interfering with code.

"The bits are not touched," he said. "There's some caveats, and as always I like to be as transparent as I can be on this: Kinect games won't work from the 360, because translating between the Kinect sensors is almost impossible."


Finally, the subject of multi-disc games was also addressed. According to Spencer, it's an issue engineers are looking into.

"We're still working on multi-disc," he said. "Lost Odyssey and Blue Dragon are some of my favourites from the 360. There's actually work in packing a multi-disc into single that requires us to go back and look at the original package on the multiple discs and reconfigure that."


Whether or not this provides you with a reason to consider the Xbox One is, of course, up to you, but it’s certainly one more check mark that the PS4 doesn’t currently have.

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-BlitzKrieg-Posted:

Inspiring confidence. Good work MS

OwenPosted:

Still don't know if I'm going to get an Xbox one yet

SahvidgePosted:

I was never planning on getting an Xbox One but Microsoft is really starting to change my mind haha

She-DevilPosted:

This is amazing. Another great reason for me to get an Xbox One. Maybe I could rock some old-fashioned MW2 while using my Xbox One (when I get it haha)

xWizPosted:

Cant wait for this update :)))

GamPosted:

Would like to see my Black Ops 2 come back into my hand lol.

SwizzlePickPosted:

Would like to see some good X360 games, So far it seems like a bunch of arcade games. I wanna see Halo Reach, Black ops 2, Red Dead, Cod 4, Castle Crashers. Now we just wait for the list to expand.

ConsolePosted:

Tree_Fiddy But what they don't say is that you need Xbox live to play online on the 360 games.... I'm getting live from another account from my friend who uses my Xbox. So I can play online on Xbox one, but not on the emulation? Fix it Microsoft...... I don't wanna pay for live when I can get it for free :/


Stop being a **** el cheapo dude, Just pay for gold $50 a year if you cant spare that then maybe you should save up and get a PC. or are you piggy backing off of your neighbor's WIFI?

I on the other hand think this is very interesting. Checkmark for Xbox.

SkyPosted:

ThomasTheDankEngine Cant wait for this but they need to add more games such as mw2 not just crappy arcade games
yes !! And call of duty 4 and world at war

EternityPosted:

ThomasTheDankEngine Cant wait for this but they need to add more games such as mw2 not just crappy arcade games


Yea, the list is slim at the moment. But it's just a matter of time before all the big titles get on board. They are already working on some of the more popular titles. You can actually go to the Xbox feedback website and vote for the games you want most. MW2 is quite high on the list at #5 (behind Red Dead, BO2, Skyrim and Halo Reach). Pretty much its just a matter of Activision giving them the ok to support MW2 on the emulator side.