Behind The Xbox One X’s Architecture Part 3 – What Are The Benefits of 12GB GDDR5 Memory And Auto Supersampling

Our final analysis of the Xbox One X’s architecture takes a look at the memory and supersampling functionality.

Posted By | On 16th, Oct. 2017 Under Article, Graphics Analysis

Well, here we are with the last in our three-part deep dive into the Xbox One X’s hardware (check out Part 1 and Part 2). The processor and GPU upgrades to the One X enable it to run games at 4K with performance levels broadly comparable to entry-level 4K hardware in the PC space. But there are two further pieces to the puzzle: first, how do you cope with the additional memory demands at 4K and second, how do you make hardware that’s built around offering a great 4K expereience compelling to the still-large audience of people with 1080p television sets?

VRAM requirements in games have only increased of late. Whether or not developers are actually making use of those mammoth framebuffers is questionable, though. As the owner of a 4K TV and a GPU with 4 GB of VRAM that was supposedly built around 4K experiences, I most certainly do have an axe to grind here.

Considering that the Xbox 360 and PS3 had a fraction of a fraction of the amount of video memory onboard the eighth-gen consoles, the lower texture resolution in older games is quite understandable. With the advent of the eighth-gen in 2013, developers suddenly had a lot more VRAM to play with. However, cross-gen titled fundamentally required assets to work on 7th gen titles without being excessively compromised. This led to an interesting situation where texture work in many 2013-2014 games was admirable while keeping VRAM usage to  reasonable levels.

Excessive VRAM usage in recent games is peculiar because the artwork’s just not justifiably detailed for the amount of VRAM consumed. Titles like The Witcher 3 and, surprisingly, Assassin’s: Unity feature wonderfully detailed texture work on models and the environment, while keeping VRAM utilization at or around 3 GB when running at 1080p. Even my heavily modded Skyrim installation doesn’t runs just fine with the Fury’s 4 GB of VRAM. Alas, in the past couple years, with 8 GB of VRAM became a tickbox feature, VRAM usage has shot up with little to show in terms of enhanced quality–Fallout 4 with its 50 GB “HD” texture pack looks nowhere near as sharp as modded Skyrim. And of course, it stutters. Having run plenty of titles both at a native 4K and 1080p, there just isn’t that great  difference in texture quality with newer VRAM-hungry titles. With 8 GB of VRAM seemingly standard now, games appear to be using the extra memory primarily for caching, not for displaying objectively higher res artwork. And of course, when scaling these titles up to 4K, VRAM requirements shoot straight through the roof. For better or for worse, this is the environment that the Xbox One X arrives in.

Microsoft’s inclusion of 12 GB of VRAM on the Xbox One X is as much a matter of necessity as it is a marketing bulletpoint. Out of this 12 GB, the GPU will be able to utilize up to 9 GB at any given point of time. Do games really use up that much VRAM? Well, it turns out they do. On a GTX 1080, Deus Ex: Mankind Divided uses up all 8 GB of VRAM. Fallout 4 uses over 6 GB. The pattern’s easy to see here, and that number’s only going to go up. Furthermore, compared to PC, the Xbox One X has a further limitation, which is that its memory is shared pool, accessed by both the processor and the GPU. While upto 9 GB can be utilized by games at a given time, in practice increasing RAM requirements will mean that 7-8 GB at most would be available at a given time. Whether or not the way VRAM is being utilized in an optimal way in today’s games, the Xbox One X has enough to offer the top-tier PC experience, in terms of texture quality, and this is a meaningful edge over the PS4 Pro.

The Pro has 5.5 GB of memory available to games, in total, which means less than 4 GB of video memory in practice. This is a real problem at higher resolutions. In PS4 Pro enhanced games, the Pro version features a signficant bump to resolution compared to the original PS4, but texture assets remain identical between the two versions. The whole point of 4K is being able to resolve more detail: simply scaling up 1080p assets doesn’t do anyone any favours. In contrast, Forza Motorsport 7 on Xbox One X was eye-opening and showcased textures that are in line with PC’s highest setting. With VRAM requirements increasing, the Xbox One X’s 9 GB of addressable video memory will play a crucial role in enabling the system to offer a convincing 4K experience in a world where 8 GB PC graphics cards are increasingly common. Moreover, with memory bandwidth scaling with resolution, the bump to 326 GB/S of bandwidth will help prevent bottlenecking at 4K, enabling the One X to hit that crucial 30 FPS update when running games at 4K.

The second question we’re looking to answer is just as important, though it’s more a matter of functionality than hardware capability. 4K is clearly here to stay. 4K TV sets experienced a 105 percent growth rate in 2016, and as of May this year, 16 percent of US households owned a 4K TV. The flip side to this is that 84 percent of US households don’t. 1080p is still where it’s at for the next couple of years. While the Xbox One X is positioned as a product meant to address the 4K audience, it’d be downright foolish not to offer value added for people still gaming on 1080p TVs. Moreover, at the end of the day, low-level optimization aside, that “6 TFLOP” GPU and “custom” Jaguar processor are not much more powerful than an RX 480 paired with something like an FX-6300. This imposes hard limits on just how much the One X can accomplish at 4K as games become increasingly complex. Lower resolution options, right down to 1080p are critical for the One X to remain a viable gaming platform into the early 2020s.

The PS4 Pro adopts a less-than-optimal approach to 1080p. Its “boost mode” utilizes just half the GPU cores, albeit at a slightly higher core clock, offering around 14-percent better framerates in GPU-bound situations. In titles that are CPU-bound, the uplift in framerate is greater. But still, at the end of the day, the vast majority of PS4 titles are framerate locked, and boost mode just enables titles to run at the framerate that they really ought to on the base hardware. In terms of supersampling, Sony puts things in developers’ hands. Some studios do offer really value added at 1080. Some games that support the PS4 Pro feature a performance mode with an unlocked framerate, as well as a mode that enhances visual settings, bringing visuals more in line with the maxed-out PC version at 1080p. Supersampling is also on the table for a flawless image quality. The caveat here, however, is just that: it’s up to developers to enable supersampling and high framerate modes on the PS4 Pro, and many opt not to bother, which is ridiculous considering that a game downsampled from 4K would performing exactly the same as it would at a native 4K.

The Xbox One X offers support for supersampling right out of the box. While it’s debatable as to whether or not this is an ideal use of GPU resources, at the very least, it ensures that gamers at 1080p have convincingly enhanced image quality over the base hardware. Moreover, the One X offers a “boost mode” of sorts as well, making higher or more consistent framerates an option as well.

The One X’s increased memory pool and enhanced support for 1080p displays rounds out the console’s capabilities, ensuring that just about everyone will have a meaningfully better experience on the One X. We’re usually (very) leery about console hardware, but from what we’ve seen so far, the Xbox One X appears truly positioned to offer the kind of compelling 4K experiences that have been the exclusive remit of high-end PC til date. Let’s see how things pan out in November!

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