Behind The Xbox One X’s Architecture Part II – CPU Improvements, DX12 Support And Improved Command Processing

Our in-depth look at the Xbox One X’s CPU and its many features.

Posted By | On 09th, Oct. 2017 Under Article, Graphics Analysis


Back to our Xbox One X deep dive! While the massively upgraded GPU is the Xbox One X’s highlight, it’s not the only component that’s seen a significant upgrade over the Xbox One. Similar to the PS4 Pro, the One X’s CPU sees a roughly 30 percent increase in clockspeed. While Microsoft speaks of extensive customizations to the CPU cores, from a performance standpoint, we’re still looking at Jaguar, though, of course, clocked considerably higher.

The CPU’s never been a strong point for contemporary consoles, and this has, in many ways, dictated the shapes that games took. Eighth-generation titles (and we most certainly still are in the eighth-gen) don’t play fundamentally differently from 7th-gen titles: in terms of world-building, in terms of interactivity, AI behaviours, things are very much an iterative step up from what came before. Higher frame rates are not possible without severe compromises with resolution. That is why you have games like The Witcher 3 running at checkerboard 4K on the PS4 Pro due to the incremental upgrade in GPU but it doesn’t achieve 60fps because the CPU is still pretty much outdated. Some might say the Xbox One’s and PS4’s Jaguar cores were too weak, even to run the games designed for these platforms. Poor performance manifested in sub-30 FPS framerates in many titles, the CPU being the main bottleneck.

This was best illustrated by Assassin’s Creed: Unity. 2013’s Assassin’s Creed: Black Flag was a cross-gen title, with well-received PS3 and Xbox 360 ports. In terms of scale, Black Flag’s urban environments weren’t significantly more dense or detailed than older titles in the series. Unity was more of a sea change. Ditching support for last-gen platforms, Unity featured an unprecedented level of detail for an open world title. The series’ signature NPC crowds were elevated to hundreds of individuals on screen at a time, and to top things off, many buildings now featured explorable interiors. This was a true generational leap over the previous years’ efforts. The problem was, it only ran at a playable framerate on PC. In interviews, Ubisoft themselves blamed the weak Jaguar CPUs for Unity’s dismal performance.

Also, the weak Jaguar cores are the reason why there are so few 60 FPS titles on 8th-gen platforms: with games like Alien: Isolation, there’s certainly enough graphics grunt to hit 60, but the processor just can’t keep up.

From a CPU perspective, the Xbox One X doesn’t aim to fundamentally alter these equations. Rather, the 30ish percent clockspeed bump will enable the processor to be fast enough to provide a more consistent expeience at target framerates: 30 FPS titles will more consistently hit their target without dropping frames. 60 FPS titles have also been somewhat hit and miss on console, with fast-paced shooters often dropping into the 40s and 50s. With its upgraded CPU the Xbox One X will be able to provide a much more consistent experience. Moreover, in cases where games are GPU-bound, the Xbox One X is capable of bringing 1080p/60 FPS to the table.

While CPU power in and of itself doesn’t get a massive boost, the Xbox One X has a further trick up its sleeve in the form of tighter integration with DirectX 12. A graphics API essentially sits in between the graphics driver (which tells the GPU what to do) and the application–the game.

xbox scorpio

Microsoft has been touting the DirectX 12 API as a solution for performance woes for quite some time. Offering closer to the metal access to hardware reduces API overhead, thus freeing up valuable CPU cycles. While games supporting DX12 have been out for quite some time, the verdict is still quite mixed, at least in the PC space. Most titles offer a small but tangible performance boost when running under DX12, compared to DX11, although a handful suffer from performance regression. A good chunk of the blame lies on economics: for better or for worse, Nvidia continues to hold the lion’s share of the consumer GPU market, and Team Green’s been notoriously tardy in implementing DX12 features, such as asynchronous compute, into their hardware. Asynchronous compute enables a GPU to simultaneously handle compute and rendering operations, substantially increasing efficiencies. AMD’s GCN architecture has featured hardware ACEs (Asynchronous Compute Engines) as far back as the Radeon 7970. The ACEs weren’t much more than wasted die space in the DX11 era. With the outing of the eighth-gen consoles, with GCN-based graphics hardware, things changed substantially–the consoles’ weak CPUs forced developers to offload compute functions to the GPU, something that the ACEs in Radeon cards are well-suited for.

Because the Xbox One and Xbox One X both utilize DX12, developers have a tangible reason to build games from the ground up, optimized for DX12. When this has been done, as is the case with Gears of War 4, the results speak for themselves: enhanced visuals and terrific performance. As developers increasingly make the transition from DX11 to DX12, DX12 performance will undoubtedly increase. In this respect, Microsoft done a good bit of forward thinking: high frequency API calls are implemented directly into the GPU’s command processor.

xbox one scorpio

The positive performance implications of this mean that the Xbox One X’s GPU can run toe-to-toe with higher-performance GPUs like the 1070 in games that are built from the ground up with DX12 in mind–as Forza Motorsport 7 has gone to show–In DX12 benchmarks on PC, the $400 Vega 56 pulled ahead of Nvidia’s 1080 Ti by nearly 20 percent at 1080p, and leveled with the 1080 at 4K. The Xbox One X was also seen running the game remarkably well, its 4K/60 FPS output better than what the GTX 1070 can offer. Forza Motorsport 7 offers a tantalizing glimpse of what the Xbox One X can deliver with the DX12 titles of tomorrow, punching well above its weight and offering performance parity with high end parts like the 1070. As an aside, the adoption of DX12 is also something of a final hurrah for owners of older GCN flagships like the Fury. 4GB framebuffer aside, I’m sure all ten of us are looking forward to the improved performance in upcoming games.

As we’ve demonstrated, a spiffed-up GPU isn’t all the Xbox One X has to offer. Stay tuned for a look at the One X’s larger GDDR5 memory pool, the One X’s cooling solution, and how supersampling will be implemented in games, as compared to the PS4 Pro.


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