*spin-off* Importance of Backward Compatibility Discussion

[function]

Oh shit, I just realised that my post is the one that spawned this entire mighty thread.

I got it wrong about the foundry, but right about everything else.

They should have let me be on the B3D podcast. Not because of anything technical, but because of my sex appeal.

 

[Nesh]

You understand slightly wrong. They are not recompiled. They are repackaged. The same orignal game executable and package is injected into a package that has the x360 system. This repackaged image is what you download from the xbox live servers.

But how do they make them run on the XB1 exactly like they did on the 360?

 

[DrJay24]

I still have some 360 and PS3 games that I havent finished. BC would have been a pleasant convenience for me if my PS4 could play PS3 games. Despite that BC wont be much used, it definitely plays a significant role in maintaining market share

That must explains why the PS3 sold so well with BC and the PS4 has been slow to sell. People buy new consoles to play new experiences. I'd rather re-buy a remaster than replay the original. BC is a great checkbox for companies and bragging point for warriors, but most people will likely never touch it. I had a BC PS3 and don't recall playing any PS2 games, maybe part of GoW2? I think I finished Fable 1 on the 360 with BC. I bet most 360 owners don't even know it can play any XB games and the PS3 sales took off as soon as they removed it because people prefer $400 with no BC to $500 with.

Now the BC for the XB1 is free to the end user, great. I have my doubts it will be used much or impact sales. I suspect it is a bit late, the generation is 1.5 year in and it makes the most difference during launch when there is nothing to play.

 

[function]

There is no future in BC.

That's why no-one buys, or ever plays, older games on PC.

 

[Nesh]

That must explains why the PS3 sold so well with BC and the PS4 has been slow to sell. People buy new consoles to play new experiences. I'd rather re-buy a remaster than replay the original. BC is a great checkbox for companies and bragging point for warriors, but most people will likely never touch it. I had a BC PS3 and don't recall playing any PS2 games, maybe part of GoW2? I think I finished Fable 1 on the 360 with BC. I bet most 360 owners don't even know it can play any XB games and the PS3 sales took off as soon as they removed it because people prefer $400 with no BC to $500 with.

Now the BC for the XB1 is free to the end user, great. I have my doubts it will be used much or impact sales. I suspect it is a bit late, the generation is 1.5 year in and it makes the most difference during launch when there is nothing to play.

I still have some 360 and PS3 games that I havent finished. BC would have been a pleasant convenience for me if my PS4 could play PS3 games. Despite that BC wont be much used, it definitely plays a significant role in maintaining market share

Thats because there were other things that were harming it even worse before the BC was dropped. Sony had to take measures to get rid of other things and dropping BC was one of the measures they had to take. BC was not removed with everything else remaining constant. Also I feel that this generation people have more desire to keep their last gen games than in the past and I think one of the reasons is the appearance of digital games.

 

[NRP]

Yep, for spawning this thread, function has secured a seat in the Hall of Badassitude.

 

[BRiT]

But how do they make them run on the XB1 exactly like they did on the 360?

They run a virtual x360 (that is setup to autorun the game) on the xbox one. No recompilation needed on the original game. If you look at the bc thread you will see the bootup sequence of the bc games includes the system turn on swish as well as the signin to xbox live toaster as well as friends online toasters etc. Its emulating the full x360 hardware (minus kinect hardware).

Each game so far that I ran also has a 256 meg file reserved, viewable from the xbox one manage game screen. This is likely mapped as a virtual hard drive that the game can use as if its a physical drive for game saves.

 

[Nesh]

They run a virtual x360 (that is setup to autorun the game) on the xbox one. No recompilation needed on the original game. If you look at the bc thread you will see the bootup sequence of the bc games includes the system turn on swish as well as the signin to xbox live toaster as well as friends online toasters etc. Its emulating the full x360 hardware (minus kinect hardware).

Each game so far that I ran also has a 256 meg file reserved, viewable from the xbox one manage game screen. This is likely mapped as a virtual hard drive that the game can use as if its a physical drive for game saves.

yes I saw the videos but I still dont understand what happens in the insides of the hardware. How are the CPU and GPU workloads allocated? Is everything run by the GPU with some of the CU's mimicking the CPU?

 

[NRP]

I assume the XBone Virtual Machine emulates the X360 CPU and GPU ISA through some type of thin hardware abstraction layer?

 

[3dilettante]

I think there would need to be some kind of retranslation, possibly caching code for later use. There are instructions like FMA that do not exist on Jaguar.

 

[joker454]

You may be mistaking importance for surprise. The announcement about backwards compatibility was a huge surprise and for some b/c is a big plus. If it's as big an issue you you seem to think it is there will no doubt they'll be a measurable increase in Xbox One sales.

It's probably too late to give a massive sales increase, the damage from the XB1 being overpriced and under powered is done. They needed this software solution at launch day, but at that time Microsoft as a company was in a state of transition so it's not hugely surprising that many things got lost in the shuffle during that chaos.

Yeah Joker, BC was so important PS3 dropped it and still managed to claw back the X360 lead (while X360 added more games to their BC list).

That's a different issue. PS3 went with hardware bc which is the completely wrong way to do it, it made the machine not easy to sell because most couldn't afford it. They had to drop it to cut costs because their launch price was astronomical. Having Xbox 360's self detonate helped them as well.

bc is one of those situations where usage doesn't equate to value.
telemetry tells them that bc is hardly used, yet one of the biggest requested features is bc.
if it helps give people a push to upgrade from a 360 to x1 then it could be very valuable regardless how much it's actually used.
there's a lot of people who's stuck with previous gen.

Yeah it's often missed that bc was the most requested feature, but people often only believe select data for whatever reason.

How much of a compromised/more expensive console are you willing to take to have the latest, greatest games play worse so that you can still play your old library? Put a dollar value on it - that's the importance of BC to you. Get an average of people's dollar values - that's the importance of BC overall.

None. As I had said many times in the past this is a software issue not a hardware issue. You don't do bc in hardware you do it in software so it should have no compromising effect on your new hardware. If your new hardware can't emulate your old hardware then your new hardware probably has other issues.

Not recompiled.

Repeat: not recompiled.

It's a genuine emulator. Kinect isn't supported though, as they can't emulate it (using Kinect 2).

Yeah I don't see how they can easily recompile it when they don't have any of the source code so I assumed it was emulation with some custom api patching going on. I was hoping that since most Kinect games probably aren't "to the metal" and use the Kinect api that maybe they could emulate the old model on the new one. But given how little they seem to care about Kinect anyways I guess this seems even more unlikely.

There is no future in BC.

That's why no-one buys, or ever plays, older games on PC.

Yup

 

[RancidLunchmeat]

That must explains why the PS3 sold so well with BC and the PS4 has been slow to sell. People buy new consoles to play new experiences.

Makes sense. Except for all the remasters that have been among the biggest sellers so far this generation. Slightly graphically improved versions of previous generation games. How is that not the same experience and not a new one?

Oh, but you covered that in your next statement:

I'd rather re-buy a remaster than replay the original.

So you'd rather pay more to play the same game and have the same experience with better graphics than play the original game for free?

Now the BC for the XB1 is free to the end user, great. I have my doubts it will be used much or impact sales. I suspect it is a bit late, the generation is 1.5 year in and it makes the most difference during launch when there is nothing to play.

Two points. 1: DIGITAL GAMES as mentioned by Azbat. If you purchased your games digitally, there's no getting up, finding the old dusty disc and loading it into your system. If you're a digital gamer, you can switch between two generations of games catalogs without getting off the couch. 2: The software sales figures provided by NPD have repeatedly shown that 360 users have been far more reluctant to upgrade than PS3 users. There's a huge population of gamers out there that MS is trying to attract. That is the population that BC is targeting.

Finally, Sony's own statements in response to the BC announcement demonstrate that they are extremely happy with the conversion rate of PS3 to PS4 gamers and don't see BC as a need for them. Their last generation users have quickly upgraded. MS's situation is very different. So looking at the announcement through the prism of the Playstation brand is going to lead you to a very different conclusion than looking at it through the prism of the Xbox brand. If Sony announced BC it really wouldn't result in a noticeable increase in sales, their base has already moved on. The 360 base has not, and the software sales demonstrate this month after month. Just because this wouldn't be beneficial to Sony, doesn't mean it isn't beneficial to MS.

 

[Rockster]

They run a virtual x360 (that is setup to autorun the game) on the xbox one. No recompilation needed on the original game. If you look at the bc thread you will see the bootup sequence of the bc games includes the system turn on swish as well as the signin to xbox live toaster as well as friends online toasters etc. Its emulating the full x360 hardware (minus kinect hardware).

Each game so far that I ran also has a 256 meg file reserved, viewable from the xbox one manage game screen. This is likely mapped as a virtual hard drive that the game can use as if its a physical drive for game saves.

That is not an indication that code hasn't been recompiled for x86. I mean Windows8 and almost all MS desktop apps came with WinRT but were recompiled for ARM. Their use of the term "repackaging" could easily be used to categorize asset re-use but with new xex's built on an x86 compiler, which run in a X360 VM that is also using x86 binaries. There is no other reasonable way for them to have accomplished this. If you were able to install a X360 game and run it, all while offline, I'd be include to believe you, but that is in fact not possible. When you insert a 360 disk, you are forced to get the digital version "re-packaged" as you say, and the disk only serves as a license check. The requirement for publisher approval, also could indicate they need access to the game source for recompilation. They are not charging publishers for the conversion work, but would need access to the code. My guess is that they've made a version of the 360 XDK for which the compiler has been re-targeted to the Xbox One hardware.

 

[Rockster]

A true emulator in the traditional sense is simply not feasible in my view due to how extensively titles made use of the larger VMX register sizes in combination with the high clock rate of the 360 XCPU, on top of the necessary endian conversion between PPC and x86, to run well enough on the Xbox One's 1.6Ghz Jaguar cores.

 

[mrcorbo]

That is not an indication that code hasn't been recompiled for x86. I mean Windows8 and almost all MS desktop apps came with WinRT but were recompiled for ARM. Their use of the term "repackaging" could easily be used to categorize asset re-use but with new xex's built on an x86 compiler, which run in a X360 VM that is also using x86 binaries. There is no other reasonable way for them to have accomplished this. If you were able to install a X360 game and run it, all while offline, I'd be include to believe you, but that is in fact not possible. When you insert a 360 disk, you are forced to get the digital version "re-packaged" as you say, and the disk only serves as a license check. The requirement for publisher approval, also could indicate they need access to the game source for recompilation. They are not charging publishers for the conversion work, but would need access to the code. My guess is that they've made a version of the 360 XDK for which the compiler has been re-targeted to the Xbox One hardware.

They have said, specifically and in multiple venues, that they are not recompiling. You may not believe it's possible, but they are really emulating a 360, in software, on the XBOne.

 

[Jwm]

There is no future in BC.

That's why no-one buys, or ever plays, older games on PC.

There are older games I would love to play on PC, some problems do exist for me to do so. a) I lost my 386 in some box b) Not all the floppies still read. I guess GOG has really helped fill those voids though, so there is a system for people to do so if they want. I came across some floppies in the garage yesterday that I remember fondly, just checking GOG and I don't see them.

Console BC - I still play Crimsom Skies from time-to-time, so I am glad that was on 360.
Xbox One BC - largely I find this worthy due to the wealth of younger E rated games that will be worth playing in the near future (3 kids). The Rare Collection is great as well, and what a value really. I do see heavy use of the X1 BC, and I like how some titles actually play better oddly.

PS2 games - the only pain here for me currently is outputs available on that console are not available in my house unless I buy a converter thing. Have not looked too much into it.

PS3 - same as X1, if PS4 would do BC outside of the streaming solution there are games I would happily play every few years. An R&C collection would be rather cool though.

I guess I was never really upset about the lack of BC going into the new generation, never a deal breaker. However, it is great to have and it helps extend the investment already made. I don't really remember caring much for BC on the playstation side, could be I have the consoles or really still boils down to what hurts my hands the most. I freely admit I lean towards one device due to comfort, and would not mind something closer in size to the old Duke.

So that is my messy take on things, and I will agree that this could help sales for X1. It will be interesting to watch, and the way the website is marketing things I bet the drive-by consumer might be confused enough to think it is already available. So an uptick in sales could happen soon. Nothing impressive on Amazon anyway.

 

[mrcorbo]

They have said, specifically and in multiple venues, that they are not recompiling. You may not believe it's possible, but they are really emulating a 360, in software, on the XBOne.

In fact, don't take my word for it. Go here and seek to about 1:31:30. Phil Spencer lays it out right there.

 

[BRiT]

A true emulator in the traditional sense is simply not feasible in my view due to how extensively titles made use of the larger VMX register sizes in combination with the high clock rate of the 360 XCPU, on top of the necessary endian conversion between PPC and x86, to run well enough on the Xbox One's 1.6Ghz Jaguar cores.

Your view is wrong. They do not recompile from source code.

 

[3dilettante]

I would like to see some technical detail on the emulation layer. There is an array of choices from straight raw PPC emulation to recompilation. Dynamic optimizing translators have been done before, such as what Transmeta or Nvidia do at a processor level, to solutions like FX!32, which profiled execution and compiles traces in native ISA to skip what would be an expensive process to do at execution time. This would not need actual source code, and it could work around code sections so targeted to the 360 that they become maladaptive to the Xbox One or even optimize code further than is possible in the original program.
Potentially, the emulated 360 download could contain as system data a set of profiles and traces to make the experience as consistent as possible early on.
Getting IP owners to sign off on the process is a general safeguard since emulation can be a gray area, but it can also provide leeway for any code caching schemes, which could be construed as copying the copyrighted work.

 

[Deleted member 11852]

It's probably too late to give a massive sales increase, the damage from the XB1 being overpriced and under powered is done. They needed this software solution at launch day, but at that time Microsoft as a company was in a state of transition so it's not hugely surprising that many things got lost in the shuffle during that chaos.

Then arguably it's not that important as a platform feature. I get how it can be very important to an individual who needs to sell their 360 to finance their Xbox One purchase and still has 360 games they want to play. That's a a given.