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Why Xbox One Backward Compatibility Took So Long (ign.com) 62

A new report from IGN this morning explains why it took so long for backwards compatibility to be supported on the Xbox One. Microsoft veteran Kevin La Chapelle says the answer to the question can be found in 2015 -- the year that Phil Spencer announced backwards compatibility at Microsoft's Xbox E3 media briefing. From the report: The fan-first feature has evolved from an experiment conducted by two separate Microsoft Research teams into a service planned for Xbox One's launch -- complete with hardware hooks baked into the Durango silicon -- until the well-publicized changes to the Xbox One policies (namely, stripping out the always-online requirement for the console) forced it to be pushed to the back burner. It's obviously back for good now, and expanding into original Xbox compatibility of select titles on Xbox One (the first batch of which we announced today). Even the Xbox One X is getting involved, with a handful of Xbox 360 games getting Scorpio-powered enhancements like 10-bit color depth, anisotropic filtering, and up to 9x additional pixel counts displayed on screen. [...]

It was 2007. One of [the research] teams was working on PowerPC CPU emulation -- getting 32-bit code, which the 360 uses, to run on the 64-bit architecture that the third-generation Xbox would be using. The other team, out of Beijing, started writing a virtual GPU emulator based on the Xbox 360 GPU architecture. "These were like peanut butter and chocolate," Microsoft VP of Xbox software engineering Kareem Choudhry recalled. "[So we thought,] 'Why don't we put them both together?'" Choudhry did just that, and so the first steps to Xbox One backwards compatibility were taken, long before the console had a name or anything remotely resembling final specifications. As Durango crystallized, so too did plans for Xbox 360 compatibility on the new machine. "This was primarily a software exercise, but we enabled that by thinking ahead with hardware," Gammill explained. "We had to bake some of the backwards compatibility support into the [Xbox One] silicon." This was done back in 2011. Preliminary tests showed that support for key Xbox middleware XMA audio and texture formats was extremely taxing to do in software alone, with the former, Gammill noted, taking up two to three of the Xbox One's six CPU cores. But a SOC (system on chip) -- basically an Xbox 360 chip inside every Xbox One, similar to how Sony put PS2 hardware inside the launch-era PS3s -- would've not only been expensive, but it would've put a ceiling on what the compatibility team could do. "If we'd have gone with the 360 SOC, we likely would've landed at just parity," he said. "The goal was never just parity." So they built the XMA and texture formats into the Xbox One chipset...

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Why Xbox One Backward Compatibility Took So Long

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  • by 140Mandak262Jamuna ( 970587 ) on Monday October 23, 2017 @08:52PM (#55420991) Journal
    It was developed by Microsoft. That is why.
  • They took a simple idea and made it complicated.
    • by gravewax ( 4772409 ) on Monday October 23, 2017 @10:18PM (#55421277)
      how so? they seem to have done what most others have failed to do, providing backwards compatibility across completely different hardware architectures (without including that hardware on the board) is no small achievement and is by no means a simple to achieve.
      • Re: (Score:3, Interesting)

        by Anonymous Coward

        how so? they seem to have done what most others have failed to do, providing backwards compatibility across completely different hardware architectures (without including that hardware on the board) is no small achievement and is by no means a simple to achieve.

        (1) They did include at least some backwards compatibility in the hardware (XMA audio and the textures format) which may or may not have been necessary. (2) The whole point the GP was making was precisely that they didn't go the simple route: inclu

        • by dstyle5 ( 702493 )

          So, we can commend them on their efforts to do most of it in software? Sure. We can even be impressed, even though it sounds like they're going through and making special optimizations per game because a generic emulator won't do the job. It's still not as good as the real thing. All the claims of better? I doubt it. I used to be a really big fan of emulation. And at first, it seems quite amazing. Over time, though, it's very clear that emulation has many weaknesses and even doing per game optimizing and ch

        • At Nintendo we did indeed include older hardware on our handheld platform for compatibility. The old hardware made for a great co-processor. Then there is this other way to do provide backward compatibility [google.com].
      • by Bert64 ( 520050 )

        Sony also have a software emulator, although the early PS3 hardware included a complete PS2 because the software emulation wasn't ready at the time.

    • by Nemyst ( 1383049 ) on Tuesday October 24, 2017 @01:29AM (#55421797) Homepage
      As opposed to not doing it at all, like Sony with the PS4? As opposed to doing it poorly, as Nintendo did with the WiiU, or not at all, with the Switch? I'm sorry, I know hating Microsoft is Slashdot tradition, but they're the only ones doing this properly this generation. Sony's farmed it all out to a game streaming service and Nintendo just has you buying Virtual Console games over and over again or, back in the day, they bundled the Wii in the WiiU with all the shitty graphics and poor resolution that implied.
  • Now that there's a BC emulator, I guess I won't be finding unwanted original Xbox games for pennies anymore. At least I amassed a good pile of games from back when I was ripping them into a chipped and juke-boxed Xbox. (Why pirate when the original disc is cheap?) I still have my two chipped Xboxes somewhere.
  • Nobody writes direct to hardware anymore, surely. It's all DirectX library calls.
    • No because GPUs instruction sets are baked into the GPU drivers which the CPU processes naturally. You just need the OS, program, and drivers to be in the native CPU instruction set. Otherwise we'd have to get new programs or recompile every time you changed GPUs!
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  • by Zaphod The 42nd ( 1205578 ) on Tuesday October 24, 2017 @12:40PM (#55424421)
    32 bit instructions should run natively on 64 bit, so the real issue here was PowerPC emulation not bits.
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