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Xbox Series X back-compat tested: up to double the performance in the most demanding games

UPDATED: More tests including Ark Survival Evolved, Just Cause 3, RDR2 and Assetto Corsa Competizione.

UPDATE: Sometimes, we just can't leave well enough alone. I returned to Xbox Series X to take a look at more Xbox One and Xbox One X titles running under backwards compatibility, as Microsoft releases more games to journalists in its preview programme. It's an opportunity to check out some of Xbox One's most challenging games, including one of the most CPU-limited games of the generation - Just Cause 3. Can the power of the Zen 2 CPU architecture rid an excellent title of its terrible performance problems? The answer is yes. On top of that, we look at games like Ark: Survival Evolved and Assetto Corsa Competizione - the hardcore driving simulation that fails to impress mostly because of its performance issues.

On top of that, we take a look at games that don't benefit so much from the new machine - mostly owing to them already being well optimised for the performance targets they have - Red Dead Redemption 2 being a good case in point. However, this does mean that some big opportunities for genuinely transformative experiences don't happen. So, Batman: Return to Arkham is still limited to 30fps in Arkham City while Arkham Asylum retains its baffling 45fps frame-rate cap. Clearly, it's still the games that have unlocked frame-rate modes that benefit most: The Evil Within 2 delivers a night and day improvement, while The Vanishing of Ethan Carter can finally be enjoyed at a locked 60fps at native 4K resolution.

We also take a look at Rainbow Six Siege - a benchmark game of sorts. To our knowledge, it's the only game on Xbox One that can actually run with v-sync fully enabled and frame-rate totally unlocked (in single-player modes at least). It's also got its own in-game frame-rate counter, allowing us to see how both Xbox One X and Series X compare in identical content. Oh, and finally, we look at a transformative experience of another sort. Ninja Theory's Hellblade has a 60fps mode that produces very blurry visuals on Xbox One X. The same code with 2x GPU performance delivers a night and day improvement.

Cover image for YouTube videoXbox Series X Back-Compat: Red Dead Redemption 2, Ark, Just Cause 3, Assetto Corsa Competizione!
Here's the second wave of Digital Foundry backwards compatibility tests on Xbox Series X. Next stop: Xbox Series S...

Original story: Today, we can lift the lid on just how powerful Xbox Series X is when it comes to backwards compatibility - and to cut a long story short, it's hugely impressive. As we write, Microsoft is still validating individual Xbox, Xbox 360 and Xbox One titles for use on the system, but we've still got a vast range of games to get our teeth into: titles that gives us some idea of just how potent the new console's back-compat capabilities are. However, it's important to stress one thing: while Series X runs old games with full clocks, every compute unit and the full 12 teraflop of compute, it does so in compatibility mode - you aren't getting the considerable architectural performance boosts offered by the RDNA 2 architecture.

Our test system arrived last week, and Microsoft describes it as being non-final hardware - indeed, it's labelled as a prototype on the back. However, I suspect that this is as close to an actual retail product as we're going to see pre-launch and before we talk about backwards compatibility, I feel it's worth reminding everyone about the innovative design, the ultra-quiet performance and its remarkable construction. The engineering team really has done a tremendous job.

In terms of this initial focus on backwards compatibility, I'm sure someone will pop up suggesting that this doesn't really matter for a new console. However, I genuinely believe that this is a poor argument. First of all, the idea of a library of games that stays with you across all the generations is obviously a good thing both for the user and for the idea of preservation in general. Secondly, Xbox Game Pass is so important now and the existing Xbox library plays a key part in that. Finally, while it may be somewhat off-brand to suggest so, I'm not 100 per cent convinced that this generation is anywhere near as tired and decrepit as Xbox 360 and PS3 were at the same point back in 2013 - the enhanced consoles have given a new lease of life to the generation and with titles like Doom Eternal and Modern Warfare 2019, games still look great. Xbox Series X then takes those stunning games and doubles the horsepower available to them, while comprehensively addressing the poor CPU performance of the current gen era. Put simply: Microsoft is right, your games can look better and run more smoothly - and that's before we factor in the power of the SSD.

Iterative improvements will be the order of the day for many games though - at least in the short term. Titles that hit their performance targets on Xbox One and One X will continue to do on Series X, so looking at the classic Rise of the Tomb Raider, its 4K quality mode still caps to 30fps, you just get a lot to that performance target. Doom Eternal runs beautifully already, but the Series X GPU will max out its dynamic resolution scaler. Modern Warfare 2019? The performance issues seen on Xbox One X are gone and with the surfeit of GPU compute on offer, expect dynamic resolution to maxed. All of which perhaps makes my task more challenging - as I was looking to get a quantifiable measure of just how much more power Series X gives library titles.

Cover image for YouTube videoXbox Series X Backwards Compatibility Tested - And The Performance Is Extreme
The Digital Foundry analysis on Xbox Series X backwards compatibility. We push the feature hard to reveal how much power you're getting for this key feature.

And I'm not even sure the increased CPU power available to old games can actually be measured because Series X blitzed every single CPU-limited gaming scenario I could come up with. Rise of the Tomb Raider's 60fps performance mode is fairly lamentable on Xbox One X - developer Nixxes drops back resolution to 1080p, leaving the AMD Jaguar cores brutally exposed with wobbly performance from the mid 30s upwards. Even in the benchmarking crucible that is the Geothermal Valley, Series X locks doggedly to 60 frames per second. There's exactly the same level of CPU-limited woe in Final Fantasy 15's 'lite' mode when run on Xbox One X, which follows ROTTR's formula of running at 1080p, unlocking frame-rate and leaving the CPU looking decidedly sheepish. Video cutscenes apart, once again we are locked at 60 frames per second.

And yes, even the Paris stage in Hitman - another example of where none of the current-gen consoles have the horsepower to deliver much more than 30 frames per second - is mostly a lock at 60 frames per second, despite the huge NPC count in the crowds. However, at the beginning of the stage, Hitman doesn't quite hit a full flat-out level of performance. We've found our first signs of a limit and it's one we can explore a little more in the sleep suburbs of Whittleton Creek in Hitman 2. In 4K quality mode with the optional 30fps cap removed, it acts as close to a console benchmark as you can get - and even on Xbox One X, this stage can dip beneath 30 frames per second. Scaling on Series X adjusts dynamically depending on content but we're looking at anything between 75 per cent to over 100 per cent more performance. There's been some discussion - prompted by Mark Cerny no less - of how developers may struggle to scale workloads over many compute units, but in many of our tests, we saw point blank that this is exactly what is being delivered.

Another eye-opening example of sheer GPU brute force comes from Dead of Alive 6. Its 4K graphics mode performs terribly on Xbox One X - operating mostly in the mid-30s. It's precisely what you don't want from a precision fighting game, and so the only real choice is to drop back to a lower resolution mode, even on the what is still currently the most powerful games console on the market. I used matched replays to compare One X and Series X. In all three of my test scenarios, Series X hit full frame-rate.

But we shouldn't expect Series X to act as a 60fps saviour for all games. While Microsoft's compatibility team has a track record in delivering technical miracles - and is talking about 4K versions of 1080p Xbox One S games and double frame-rate modes - by default, if a game has a 30fps performance cap, 30fps is the best you're going to get. Even so, there are games that do unlock frame-rates to often disappointing effect: Monster Hunter World is a classic example of a stunning game that is let down by inconsistent performance. Again, the improvement from Series X is transformative, mostly doubling performance in the highest specification resolution mode - and after this, it's difficult to go back. Certain effects do see Series X frame-rates drop though: it's worth remembering that from Xbox One to One X to Series X, we've seen tremendous increases in GPU compute power, but memory bandwidth has not risen in step.

There may be the some consternation that Series X back-compat isn't a cure-all to all performance issues on all games, but again, this is the GPU running in compatibility mode, where it emulates the behaviour of the last generation Xbox - you aren't seeing the architectural improvements to performance from RDNA 2, which Microsoft says is 25 per cent to the better, teraflop to teraflop. And obviously, these games are not coded for RDNA 2 or Series X, meaning that access to the actual next-gen features like variable rate shading or mesh shaders simply does not exist.

We should take the results seen here for what they are - a gigantic level of additional horsepower being delivered to our existing library of games, with often transformative effects. So, the mythical 60 frames per second lock on Sekiro: Shadows Die Twice still isn't quite achievable, but it's still the best way to play the game on console bar none - and the 50-60fps playback says to me that this could be a game that really stands to benefit from support on variable refresh rate displays, something I'm really looking forward to testing.

Transformative is a word that often came up when I tested backwards compatibility on Series X - and this can extent to OG Xbox and Xbox 360 titles too. Unfortunately, not many of them are available on the selected range of titles available for testing right now, but one game did catch my eye: Grand Theft Auto 4's performance issues on original hardware are the stuff of legend. In fact, actually understanding its frame-rate is the reason I developed frame-rate analysis tools in the first place. Meanwhile, its back-compat support on Xbox One and Xbox One X isn't particularly great. As the game runs unlocked, One X can power its way to 60fps in graphics heavy scenes, then see performance collapse when the CPU is tested. It produces a highly variable experience and in some respects, even Xbox 360 runs it better. This all changes with Series X which not only locks to 60 frames per second in every scenario I could test it on, it does so with HDR.

More specifically, it's using Auto HDR - an AI algorithm that maps existing SDR content into HDR space. It works on most non-HDR games and I'm intrigued to see how it plays out on more games. From what I could see, the desired effect was achieved on Grand Theft Auto 4, but there were some odd effects - a character in bright white jacket saw that blown out to ultra-white effect while the white road markings seemed to have a bit of an unnatural glow to them. Microsoft is actually disabling Auto HDR on titles where it feels the effect doesn't quite work, but I'm eager to test this on more content.

Cover image for YouTube videoXbox Series X Complete Specs + Ray Tracing/Gears 5/Back-Compat/Quick Resume Demo Showcase!
Our original Series X specs reveal shows aspects of backwards compatibility we've still not seen - such as 4x resolution improvements to a non-X enhanced title, Gears of War Ultimate Edition.

As for the SSD? This can help tremendously too. Load times in the area of one minute when accessing saved games on Final Fantasy 15 were chopped down to 12 to 14 seconds. I also think that Xbox Quick Resume really is a beautiful piece of technology - effectively working in the way that emulator save states dump system memory to storage, then load them back to bring you back to exactly where you were in the game. I love the idea of the 'instant loading' being promised for next-gen games but are we really going to see developers and publishers bin off extended logo screens and intro sequences? Quick Resume puts you straight back into the game - the system itself simply acts as though you've pressed the pause button. Interestingly though, I did note that the 6.5 second loading times I saw at Microsoft HQ back in March are now around 12 to 20 seconds. It's true that I was using different games, mind you, but as great as it is, it's not quite as immediate as it felt during my time at the Redmond mothership.

But that's where I am with Xbox Series X backwards compatibility - and I'm hugely impressed by the results. The boost to system performance compared to Xbox One X is clearly tremendous and I'm liking Microsoft's commitment to the Xbox library and putting so much resource into producing results like the ones I've detailed today. Right now, I think that Series X back-compat delivers circa 2x GPU power, limited perhaps a touch by memory bandwidth, and offers what amounts to a bottomless pit of CPU resources to the point where I don't feel I hit processor limits at all during my tests. The fact that Microsoft is talking about 4x resolution multipliers and double frame-rate upgrades says to me that the firm knows there's something special here - and I really want to see these features deployed as broadly as possible. The dream would be to see frame-rate unlocking as a system level feature, just as Auto HDR is.

I'm also curious to see how Xbox Series S backwards compatibility will land. If I can't yet find CPU limits in existing games, the chances are I won't be able to find it with Series S either. And from a GPU perspective, while the Series S GPU runs at four teraflops vs the 6TF in One X, it should actually be able to deploy more power at older games. Xbox One X split vertex and pixel shading across its 40 compute units, essentially delivering 3TF of performance - a limit that does not apply to Series X or Series S. Overall though, what we've learned today is that Xbox Series X backwards compatibility delivers some eye-opening results - but it's how Microsoft aims to deploy that power beyond what we've seen today that fascinates me most.