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Xbox Series X: the new information on the SoC and the difficulties with ray tracing

During the Hot Chips event, the powerful hardware of the Xbox Series X was almost completely exposed: let’s analyze it in detail starting from the sophisticated SoC it mounts.

The hardware of Xbox Series X was almost permanently laid bare during the Hot Chips event, the annual symposium dedicated to high-performance chips. Not all the information that emerged is easily interpretable, but there was no lack of confirmations, images and new information that can help us understand the actual potential of the awaited and undoubtedly powerful Microsoft console. Let’s start from SoC in our analysis and then go into more detail of some highly anticipated features, such as ray tracing.

All the numbers of a 15.3 billion transistor SoC

Microsoft has used the Hot Chips event to show us images and details of the Xbox Series X SoC, a console that focuses on the brute power of the RDNA2 GPU but does not miss a long list of optimizations and current technologies such as ray tracing and ‘artificial intelligence. The total number of transistor is 15.3 billion against the 6.6 of the Xbox One X, but the use of 7 nanometer transistors has allowed AMD to reduce the space of the the compared to the 367mm of the previous console. In fact, we are talking about 360.4 square millimeters that include an 8-core and 16-thread Zen 2 CPU flanked by an RDNA 2 GPU which, predictably, occupies a large chunk of the overall space, extending for 47.5% of the chipset.

On the other hand it is at 56 compute unit that make it up, 52 active and 4 probably used for redundancy, which will touch the bulk of the work in a generation that aims at 4K at 60fps, pushing up to 120fps with titles like Halo Infinite that chase the PC on the level of competitive multiplayer. The goal, however, is undoubtedly within the reach of a hardware that has 30% of active compute units in more than one RX 5700 XT, reaching 3328 streaming processors pushed to 1825Ghz. For bare and raw capacities we should therefore find ourselves on the part of an RTX 2080 SUPER, with all the extra optimization allowed by the closed environment of a console that also allows you to take advantage of the SSD to lend a hand to the 16Gbps of memory, as we know for some time now divided between 10GB at 560GB / s and 6GB at 336GB / s.

However, the role of the CPU which, four times more powerful than that of Xbox One X, guarantees responsiveness to the system and, when properly exploited, can also lend a hand with physics and artificial intelligence. Among other things, it seems to have two operating modes, one at 3.6GHz with active multithreading and one at 3.8GHz giving up the 8 additional threads. But there are other technologies that interest us most in terms of game optimization possibilities. One is theSSD which, although slower than the competition, reaches 2.4GB of transfer speed with uncompressed data but can go up to 4.8GB / s with data compressed by dedicated hardware that is part of the technology Xbox Velocity Architecture, undoubtedly designed to guarantee instant and uninterrupted open world loads, but also to reduce the space occupied by games on the disc. Among other things, all this is also valid for the additional storage of the Xbox Series X Storage Expansion Card developed by Seagate and Microsoft to guarantee the same advantages of the internal NVMe PCIe 4.0 SSD.

Xbox Series X Hardware Slide 4

Optimizations, secrets and infrastructure

All seasoned with the technologies we know as the Mesh Shading and the Variable Rate Shading, which allows the system to concentrate the power on the relevant areas of an image avoiding wasting resources on less visible areas, and by some novelties such as the GPU Work Creation, designed to squeeze the GPU to the bone. There is also talk of a Sampler Feedback streaming that can be implemented very easily, which is useful for developers to optimize memory according to textures, and of Machine Learning Inference, with the ability to use the FP16 calculation also to apply what has been learned from a AI algorithm even on new data. Not bad considering that we are talking about a theoretical power pool of 24TFLOP from which to draw to improve the artificial intelligence and maybe even the performance.

There do not seem to be, it must be said, hardware blocks dedicated to Machine Learning on the Xbox Series X SoC, but surprises, perhaps similar to the NVIDIA Tensor Cores, by a Microsoft that on the hardware level seems more than calm are not to be excluded, so much so that not even pushing the frequencies to the extreme to get even more high-sounding numbers. Instead, he underlined the parallel cooling to which we owe the shape of the console and a rich outline designed to guarantee the maximum in every sector and which we have already talked about which includes reduced controller latency, Dynamic Latency Input (DLI), Auto Low Latency Mode (ALLM), Variable Refresh Rate (VRR), Quick Resume, Intelligent Delivery and Smart Delivery, with hardware dedicated tospatial audio and an automatic SDR to HDR conversion feature that promises to have no impact on CPU, GPU and memory. On the other hand, ray tracing could be very heavy, the protagonist of some not particularly exciting official statements.

Xbox Series X Hardware Slide

Ray tracing, a spectacular technology but …

Xbox Series X, we know, is equipped with hardware dedicated to ray tracing, the main novelty of the RDNA2 architecture, and enjoys full support for the DirectX Raytracing (DXR) API, the DirectX Ultimate component designed to push realistic lighting towards widespread diffusion. But it may take longer than expected to fully enjoy the wonders of a technology that, when applied massively, is definitely difficult to manage even for high-end hardware. On the other hand we are talking about millions of rays of light that interact with countless surfaces to create an almost real illumination between lights, shadows and refractions whose rendering is also influenced by the color and material of the reflecting surfaces. Enough, in short, to put a 14.2TFLOP power card like the GeForce RTX 2080 Ti in great difficulty.

Of course, we hope that the latest technology for ray tracing of RDNA2 GPUs is more advanced than that pulled out by NVIDIA two years ago, but we must take into account that we are talking about a technology that is still new for many developers and that we are talking about hardware destined for cost less than a mid-range PC. We are not surprised, for this, in front of the words of Mark Grossman, the system architect of Xbox Series X who talked about the tendency of several developers, at least at this time, to prefer the classic rendering techniques, using the ray tracing selectively not to sacrifice too many hardware resources.

Xbox Series X Hardware Slide 2

But even classical lighting has made significant strides towards dynamism, as we have seen with the Lumen technology of theUnreal Engine 5, and the combination of several techniques could still give remarkable results. Furthermore, developer resistance could be a symptom of the poor ray tracing acceleration capabilities of the Xbox Series X hardware, but it could also depend on the lack of familiarity of the software houses with a technology that is new and evolving. In Microsoft’s slides we read numbers like 380G/sec ray-box peak e 95G/sec ray-triangle peak, but we don’t know how to relate them to the millions of rays per second of the GeForce RTX. But we know that if Microsoft, like Sony, has implemented hardware technology in machines that are subject to very tight constraints between price and performance, it means that it wants to exploit it. This is why we do not worry too much in the face of understandable attempts to curb the hype, especially after the Halo Infinite case, knowing that there are those who expect full path ray tracing from a machine destined to cost a maximum of 600 euros and knowing that Regardless of the power of the hardware, we will hardly see massive applications of ray tracing in the first year of life of the new consoles.

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