Digital Foundry – ‘In Theory: Can the PS Neo GPU Deliver 4K Gaming?’

Source: Eurogamer

We’re months away from the release of PlayStation Neo and as things stand, with a marketing black-out from Sony, it’s still unclear what the purpose actually is for this faster, more powerful console. All we have to go on are leaked developer guidelines, which demand feature parity with the existing PlayStation 4. Beyond that, Sony’s recommendations to developers are surprisingly open-ended. All Neo games must render at 1080p or higher at the same performance level – or better. But beyond that, developers get to choose what they do with a mooted 2.3x boost to GPU power.

So we were wondering, just how much of a generational leap does Neo actually represent? Sony’s docs focus heavily on supporting 4K displays, but to what extent is that actually possible with the GPU horsepower on tap? We wanted to get an idea of what the new graphics core is actually capable of, so we built our own ‘Neo’ and put it to the test.

It’s not as crazy as it sounds. The leaked graphics specifications for PlayStation Neo are a match for the latest AMD graphics core, codenamed Polaris, released to the public recently in desktop GPU form as the Radeon RX 480. We’re looking at 36 compute units based on ‘improved’ AMD Graphics Core Next (GCN) architecture – just like the RX 480. The difference comes in terms of clock-speed. The RX 480 runs at a maximum 1266MHz while Neo’s GPU runs at 911MHz – a necessity for a small, closed box system.

And curiously that clock-speed is baked into RX 480’s power management set-up, rounded down to 910MHz. It’s ‘power state two’ – the second of seven power states that can be easily configured by PC users meaning that, yes, we can run RX 480 at the same clocks as the Neo GPU core. Confronted with identical gaming workloads, we can now scale up resolution to see just how far the Neo GPU can go before frame-rates become unplayable. Can we get a playable 4K experience

All the evidence collated thus far does indeed suggest that the Polaris 10 processor, pared back to Neo clocks has 1440p as the rendering sweet-spot. And that’s great, but not exactly revelatory. Sony’s Neo documentation isn’t keen on 1440p as a framebuffer target either as it’s not a great fit for a 4K display – it’s the equivalent of running 720p on a full HD screen, which doesn’t make for an impressive presentation. So do we have a problem here – a fundamental mismatch between Neo’s potential capabilities and 4K display tech? Perhaps, but perhaps not.

We benchmarked seven PC games at 1080p on console-equivalent settings or close to it, reducing texture quality where required to ensure that the R7 265’s 2GB framebuffer wasn’t a limiting factor. There are some disappointments but equally, there are some genuinely impressive results. Take the Witcher 3, for example. Our Novigrad City test run hits a 33.3fps average on the R7 265 PS4 target hardware – pretty much in line with console performance. However, the same test run on Polaris 10 at Neo spec sees a huge jump in 1440p performance, and just a six per cent drop compared to the R7 265 run at 1800p. 4K remains off the table, but 3200×1800 is essentially the 4K equivalent to a 900p upscale for full HD displays.

Rise of the Tomb Raider also sees a good result. At 1800p, we’re about 14 per cent off the pace set by our base-level PS4 equivalent hardware running at 1080p, but crucially, we’re still above 30fps. However, there’s little evidence that demanding triple A games will deliver a native 4K experience on Neo-level hardware, and some of the 1440p results (representing a 77 per cent pixel count increase over 1080p) are disappointingly low, suggesting that maybe we could do with more memory bandwidth.

The rise from PS4’s 176GB/s to Neo’s 218GB/s clearly isn’t scaling in line with the huge boost in GPU compute. But some results are showing genuine potential here, with that 2.3x increase in overall GPU power in theory allowing for something in the region of a 2x boost to base resolution. And that 2x increase over standard 1080p could prove crucial. In addition to recommending that developers experiment with standard upscaling, Sony is also talking about cutting-edge forms of pixel reconstruction – in particular what it refers to as the 2×2 checkerboard. It’s a new one on us, but eventually we found what looks to be a match in a GDC talk called Advancing VR Rendering Performance, presented by Valve’s Alex Vlachos. It’s a presentation well worth checking out as it reveals a range of clever optimisations used in getting decent VR performance from low-end GPU hardware, but it also discusses the 2×2 checkerboard technique.

In essence, the GPU uses post-processing techniques to extrapolate a 4×4 pixel block from native 2×2 rendering. In theory, this should produce a decent 4K image while requiring just a 2x 1080p pixel count (around a 2688×1512 native framebuffer, if you like). We’ve not seen the technique in action before, but Sony mentions it several times in its documentation so we should assume that its R&D masterminds believe it can produce pleasing results on a 4K screen.

 

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Motwera

Creator of 3WIREL! and Crashy News.

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