How Xbox One's Backwards Compatibility Will Work

Arguably the biggest announcement during Xbox's E3 conference was the news that Xbox 360 games will soon be playable on the Xbox One — free of charge. For gamers who still haven't upgraded their last-gen consoles, this could be the killer app that gets them over the line. As expected, Microsoft's announcement drew rapturous applause from the audience, despite offering very little in the way of details. We asked Xbox's vice president of devices and studios, Yusuf Mehdi, to explain how the platform works.

This summer, Xbox One will introduce native backward compatibility for Xbox 360 games on the Xbox One. This will be offered for "select" Xbox 360 games and will be a free service for anyone who owns the original titles. What's more, the old games will boast support for Xbox One features such as screenshots, broadcasting and GameDVR. You'll also be able to play multiplayer online games against players on the original hardware.

Initially, there will be around 100 Xbox 360 games available, although Microsoft promises continued support from third-party publishers.

"The idea is, if you're a developer and you want to get your Xbox 360 games on [Xbox One], you tell us you want them to be backwards compatible and then we get that going and we will have the games up and running," Mehdi explained to us.

So how will the feature actually work? Can you just pop in a game disc or will some sort of unique download code be required? As it turns out, a bit of both.

"It's designed to be very simple: you stick the disc in, you download the game and then you're ready to play it."

Sounds pretty good to us. If you have a supported Xbox 360 game, all you need to do is insert it into your Xbox One and you're good to go.

Before the official launch, a beta will be made available which focuses on a small batch of titles which we've listed below:

  • Banjo Kazooie: N n B
  • Banjo-Kazooie
  • Banjo-Tooie
  • BattleBlock Theater
  • Defense Grid
  • Geometry Wars Evolved
  • Hexic HD
  • Jetpac Refuelled
  • Kameo
  • Mass Effect
  • Perfect Dark
  • Perfect Dark Zero
  • Small Arms
  • Super Meat Boy
  • Toy Soldiers
  • Toy Soldiers: Cold War
  • Viva Piñata
  • Viva Piñata: TIP

Apart from Mass Effect and maybe Perfect Dark Zero, there's nothing terribly exciting in that list. It will be interesting to see how fully Microsoft commits to this service — hopefully it will eventually include most games and not just 100 or so bestsellers. We'll be keeping an eye out for backwards compatibility in action at Xbox's E3 booth tomorrow.

Kotaku travelled to E3 in LA as a guest of Microsoft.


    "Select games" huh sound like the 360... 6 months of Disney and Microsoft games then nothing and no word till it's quietly dropped.

      Sounds like you didn't read the whole article.

      “The idea is, if you’re a developer and you want to get your Xbox 360 games on [Xbox One], you tell us you want them to be backwards compatible and then we get that going and we will have the games up and running,”

      "Select" here seems to mean "the developers have to opt in, it's not automatic".

        I'd say Microsoft would charge for the privilege, it wouldn't port a Ubisoft or Capcom game out of the goodness of its heart.

          Entirely possible. We don't really know how difficult the process is, it might be really easy and cheap. It's in Microsoft's best interests for the XB1 to be ubiquitous and they may consider this a reasonable expense to encourage future sales. Alternatively, if they do plan to open X360 games for digital purchase on the store in the future, they may just take the port cost out of the sale price.

            Honestly, I think its more Microsoft not wanting to step on a publishers toes and destroy any deals they may have. Putting every 360 game on there could cause outrage from publishers who want to rebox and port to the new systems

              Exactly - I imagine the makers of Dishonored for instance,wouldn't be too thrilled that their game which was free for 360 owners some time ago would be able to be transferred in the face of their definitive edition.

          They said in the E3 press conference that it is free for all developers to opt in.

            Yes, free for developers to opt in to the process, but let's wait and see exactly how it works. I would be staggered if MS didn't extract something out of the deal. There would be a fair bit of time spent by MS on each title, otherwise they'd have rolled out the entire 360 back catalog.

              Not exactly, according to their spin machine. They said that publishers need to opt-in (not auto roll out) because licencing and distribution agreements may have changed since the original 360 game was shipped. It could be, that the publisher may no longer have the licences to songs or characters in the game, therefore they won't be able to opt-in. So from the looks of things, it's more to do with legalities.

                Yeah, I think that would be right. I was thinking more about the porting process. If it was so quick and easy to do I'm sure MS would have done before now for all its own games at least. That they haven't suggests that they either deliberately kept the Xbone non-BC to ensure a nice tail off in 360 sales, or that the porting process is not just 'flipping a switch'. The fact that the physical 360 discs require the Xbone to 'download the game', according to Phil Spencer, suggests that there is quite a bit of programming work involved for each title. That's the cost I was thinking about.

        They also said in the conference that it'll be done both on user voting (they've set up a community site for it) and by tracking activity on xbox live.

    Such a strange beta list. I have maybe 70 games on 360, and the only games on that list I have are Hexic and Toy Soldiers - Cold War.

    Which are both awesome btw.

      From a quick look over the list it looks like all those games are 1st or 2nd party. It’s probably easier to port them quickly than it would be messing with external parties codes.

      Pretty funny that many of them are from Rare (Banjo, Perfect Dark, Viva Pinata) and they’re all being re-released on the Xbone anyway…..

      Last edited 16/06/15 10:00 am

    "It’s designed to be very simple: you stick the disc in, you download the game and then you’re ready to play it."

    If I'm reading that right, it's not quite backwards compatibility - it's essentially using the disc as a code to download a version of the game that's been rebuilt somehow to work on the new Xbox? It's an interesting system - be interested to see how it plays out.

      Yeah, that's how I read it, too.

      I find it odd that it seems to be this hard, to be honest. Haven't all the Xbox consoles since the first one been fairly similar ie pretty much PC-esque architecture, DirectX, etc? I wouldn't have thought it would have been that difficult to make backwards compatibility work in that case. I guess it must be harder than it seems from the outside.

        The architecture isn't really the problem, it's most likely the fact the XB1 API is different to the X360 API. DirectX on PC is built to maintain backwards compatibility but on consoles that's usually unnecessary bloat.

        From Wikipedia, "The XCPU, named Xenon at Microsoft and "Waternoose" at IBM, is a custom triple-core 64-bit PowerPC-based design by IBM." So it's PowerPC based - the instruction sets are NOT compatible.

        On the other hand, the original XBox used a CPU based on the Pentium 3, so it should be much easier - but there's no sign MS have tried to do so; the announcement is about the 360, not the XBox.

        They're probably using something like a JIT code reassembler - or straight reassembly - there should be a few of these round from the Apple transition from PowerPC to x86, requiring mainly a few code tweaks due to changes in instruction sets.

          If anything, you'd think that the XB1 would have the horsepower to simply run a virtual machine of a 360

            You would need to use something like QEMU to run the low level instruction set conversion [emulation]. This is done in software, and is *very* slow.

            The reason virtual machines run so well is because they are using hardware virtualisation techniques, which require the virtualised system to be the same architecture as the host.

              And the reason why modern CPUs can emulate 1980s/90s CPUs of a different architecture is that modern CPUs are really, REALLY fast compared to CPUs of that vintage (as in, a hundred times faster or more.) As I recall it wasn't until the x86 line reached around 2-300MHz that it could emulate the Motorola 68k CPU in real time.

              In addition to the overhead of emulating hardware in software, emulating multiple CPU threads is enormously more difficult.

              Ergo my suggestion of a JIT recompiler (i.e. the CPU converts code into its native instruction set as it runs) - but multiple threads make that very difficult as well.

              The best option, if available, is to just duplicate the original CPUs on the new platform's CPU die; with transistor counts still increasing exponentially (albeit at a now reduced rate) due to Moore's Law, it's by far the simplest method and is why the PS1 was emulated easily on the PS2, PS3, PSP and PS Vita. However, the manufacturers may quite reasonably decide that silicon is better dedicated to new capabilities.

                That's basically what QEMU does, it emulates the instruction set and converts each instruction to the host architecture.
                You're right, it needs processors which are orders of magnitude faster than those being emulated, putting the original CPU's on the new platform is exactly what Sony did with the PS3 at launch, which had a PS2 CPU/RE chip on their.

                Of course, the same people which complain about no backwards compatibility are also the same people which complain when the console costs too much! ;-)

                  Not sure it's the same thing - AFAIK QEMU emulates the CPU (reads each instruction then performs a parallel action, essentially treating the original code as a language to be interpreted) whereas a JIT compiler creates native code to be executed (so is slower the first time code is executed, but near-native speed the second time around).

                  Of course with the PS3 the silicon was there for the initial NA release but was changed to software emulation for the European/Australian release... and eventually dropped altogether.

                  I think Australia had reason to complain with the PS3 as we received a less capable system (no PS2 silicon) but paid more for it. :-/

              Ahh yeah, I'd forgotten the architecture requirements, I was thinking purely on a software level. Shame they won't just release a plug in 360 processor, kind of like how the original PS3s had what was effectively a PS2 built in

            While the Xbox One certainly has more CPU power than its predecessor, it isn't that clear cut.

            The 360 has three PowerPC cores running at 3 GHz, while the Xbone has 8 AMD64 cores running at 1.75 GHz. So if the game was running one of those cores at full utilisation, the Xbone probably doesn't have enough single thread performance to match that, even if you ignore the losses due to emulation.

            For games that treated the 360 CPU as six cores due to the hyperthreading, they might have more luck, but you'd still be better off recompiling from source for the new architecture.

        The xbox and xbone are both based on the x86 architecture [ie: same as PC's], however the 360 uses a triple core Xenon CPU which uses the PPC architecture from IBM, which is what is also used in the PS3's PPE.

        For this reason, it was very difficult to natively run xbox games on 360, and now 360 games natively on xbone. This isn't just a software thing with different API's. It's completely different hardware at the lowest level. This means that the code needs to be completely recompiled before it will run natively, which is very non-trivial [this is what they do for the HD remasters, and requires a full dev company to perform].
        Instead, what is required is emulation [similar to what is used to play SNES games on your PC, for example]. They emulate the 360's hardware on the xbone in software. The 360's CPU, while old, is still extremely complex compared to a SNES, so I am unsure if they have got a full emulator up and running. If they did, then they could theoretically run any 360 game with just the disc. The fact they are requiring a download suggests there is some sort of recompilation process they have developed, to recompile 360 source code for the xbone.

          I'd completely forgotten the X360 ran a PPC CPU, my bad. Still, I think you're overstating how difficult it is to migrate application-level software to a different architecture and understating the API-level side effects. Retargeting a binary build is relatively simple, many compilers already support multiple architecture targets. Gregor touches on it above, but there are plenty of PPC/x86 compatible compilers around, many from Apple's transition across the same boundary.

          Converting operating systems is considerably more difficult, as is converting anything that uses inline assembly, but the former isn't relevant for application migration and the latter is becoming increasingly uncommon. Hand-made PPC assembly tweaks obviously have to be replaced with x86 ones, but that hardly requires a full dev team and it's less of a concern when the new hardware outperforms the old as thoroughly as in this case.

          API differences, on the other hand, aren't as simple as a recompile. It's rarely as simple as an adaptor interface either. The bulk of your development time on a port is spent on rewriting for the new API.

      Assets are the bulk of the content on the disc which wouldn't need to be downloaded again. Most likely the main executable needs to be rebuilt and that's the part that will be downloaded. If so, the down side is devs have to opt in to get it to work (which is mentioned in the article above) but the up side is the game will run natively, not in an emulator.

      You'll probably still need the disc to play unless the game is fully installed on your HDD.

        Seriously doubt this would be the case. Much easier for them to have one package which is downloadable for both digital and physical licenses, where the only difference is whether you need the disc in the drive or not to be allowed to start playing.

          Possible, but if that happens then they'll likely begin to sell titles on the store since the entire package will be available. They've made no indication they plan to do that, which suggests to me that it's a more restricted process at least for the time being.

            The digital titles that you own and are part of the Back Compat game catalog will automatically show up in the “Ready to Install” section on your Xbox One. For disc-based games that are a part of the Back Compat game catalog, simply insert the disc and the console will begin downloading the game to your hard drive. After the game has finished downloading, you will still need to keep the game disc in the drive to play.
            So yes, if the physical game is supported, so is the digital.

              Interesting. It seems like they're setting up for selling X360 titles on the XB1 store but they've specifically avoided saying as much. All the wording points to titles you already own, but it seems like a wasted opportunity to me to host the entire package as a digital download for people who already own the game and not go one small step further and actually sell them, ala Nintendo's Virtual Console.

    Wait, so could u just like borrow a bunch of discs you dont own and get the downloads free?

      I imagine you'll need to have the disc in the console every time you want to play it...

        Unless you already downloaded it in the first place. I think.

          If it was a digital title to begin with, that will be associated with your gamertag and, assuming that the DRM is the same as current digital downloads on the XBone you'll only be able to download and play it on the One console that you have associated as your "home" console, or otherwise while signed in as the gamertag that owns the rights.

      I assume you would need to have the disc in the drive to play the game, not just download it.

    Well I guess I'll download Mass Effect to check it out then go back to gaming. Woo?

    I still have a bad pile of shame for 360 (and all other consoles) so running them on xbone would be nice.

    It might have been arguably the biggest announcement of the MS presser if it was made a year ago, or if we were getting 100% of the 360 library. As it stands it’s just “good news”, the Xbone library is big enough now to hold its own in most cases, I’ve been playing much less 360 lately.

    Certainly kicks the shit out of Sony’s money-grubbing BC “solution”.

      I personally disagree. I have a lot of 360 titles I'd love to replay and many I've not gotten around to yet, but I find myself reluctant to actually use my 360 console which has lain dormant for about a year now.

      If I can just use my XBone instead, I might actually make some headway on my pile of shame.

      Agreed. Halo 5, destiny dlc and fallout 4 (which is killing E3 all on is own). I'll have absolutely no time or reason to go back to last get titles.
      Well played by M$ but I just don't need it.

    Didn't they say that games being added were simply a matter of publishers giving an "OK" and that no real extra work had to be done on top?

    If they allow all 360 Halo games, does that mean that the MCC will become even more irrelevant?

      Depends how you feel about graphics and shiz. I know playing from Halo: Anniversary Edition to Halo 2 was a huge shock with the downgrade in graphics even a few years back. By comparison it was so super blurry that it felt more like an N64 game :P

      So yeah I may have, literally, last night reorganized the games and Blurays I have on display. Sure I gave my full collection of Halo discs a lovely visible space to show themselves off. But personally I'll probably only play through any Halo again once I pick up the MCC.

    So its still not just put a 360 disk in and play?

    The reason for not giving 100% support is because each and every single game that runs on the X1 runs in a unique way from eachother so for them to support every xbox360 game they need to code a different emulator for each title so im guessing the devs are the ones who have to actually make it work either that or they pay a fee to port it over.

    So typical that this comes out a few days after I traded in all my 360 games lol just my luck :P

      Do you have a receipt, maybe you could get them back... kinda like how you buy something and get a refund? :P

        haha i think i do actually, as I put all the games on a preorder and still have that receipt!

    A day late and a dollar short for me. Though in fairness and from the look at that list, I'm probably not the target audience here.

    Well I know I'm not moving till my faves are compatible. There's nothing on xbone comparable to some 360 games

    Native. You keep using that word. I do not think it means what you think it means.

    And presumably publishers who have released remastered versions for the new console will decide not to participate in the program. Why let the 360 version of Tomb Raider or Sleeping Dogs compete with the remastered versions?

      well i think that probably speaks for itself

    Oh ffs, stop saying it's back compat!

    This summer, Xbox One will introduce native backward compatibility for Xbox 360 games on the Xbox One.

    No it fucking won't. It'll introduce native app download for select 360 games.

    That's it. No back compat to be seen here.

      Strictly true, but it's how Microsoft are referring to the program. The specifics of the implementation are speculative at this point, looking forward to seeing how it works under the hood once we can get some details out of the just-launched beta program.

        There is no under the hood. They'll port a couple games over and you download and play em.

        I'm just waiting for the class action lawsuit where MS are fucked for lying about back compat. :)

          "Under the hood" meaning "what they do to accomplish the task". We don't know what modifications are involved yet. Could be JIT, could be a native recompile, could be a packaged emulator (like how Steam does DOS games). I'm a software developer, I'm interested in the technical specifics =)

            Ahh. Well it's not the packaged/wrapper emulator. Current PCs can hardly run it.

            But yes, it is interesting, and to see how quickly they can pump out these ports.

            It's a virtual machine. The games themselves aren't being emulated like they were on 360 with OG BC, which is why that was dumped so quickly.

            In this case, the hard work is already done. The virtual machine is created and is downloaded with each title. For example, Hexic HD is only 55MB, but on Xbox One it's about 800MB. So the VM is around 750MB and is packed with every 360 title. So as far as the 360 game is concerned, it's running on 360 hardware.

            The tricky part comes in 2 parts:

            1) Publishers need to opt in. So luckily, with Xbox Live Arcade, Microsoft published like 90% of the library so I'd expect to eventually see just about every (non-Kinect, non-accessory) Arcade game come over.

            2) The Virtual Machine will need tweaking for some titles to make sure it's a "one fits all" solution for every title they bring across.

            It's unfortunate Kinect games and accessory based games (Guiat Hero, DJ Hero) won't make it but I can understand why, so I'll leave my 360 out in that case, but this is still a great thing they're doing.

      Actually yeah, it is. The way Microsoft described it the Xbox One is running a full Xbox 360 emulator, sounds backwards compatible to me. Hence why all they need is publisher approval for games because they are running in exactly the same environment as the Xbox 360.

    what a weird list of games to be testing... would expect some kind of flagship title on there.

    Major Nelson (the Xbox PR guy) posted this on YouTube:

    They say that the games work through the emulator running on the Xbox One. They said that some USB functionality won't be working (so any funky games that use USB devices may not work). The saves will work via the Cloud saves. Publishers needed to opt-in, rather than auto-rollout of every game because of licencing concerns (e.g. a publisher may no longer have rights to songs or characters in the game).

    Last edited 16/06/15 5:52 pm

    This already works for those on preview. Downloading my compatible games now.

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