We know PlayStation 4.5 is real - but why is Sony making it?

So what do we know about the rumoured PlayStation 4.5? In the wake of last week's post-GDC outing of the hardware by Kotaku, we have independently established that it's real and that Sony's R&D labs have prototype devices, and we also have more than one source referring to it as PlayStation 4K, the name we'll be using for now. And this is where things become slightly strange - because while more GPU power is being offered to developers, realistically it is nowhere near enough to provide native 4K gaming at the same quality level as current 1080p titles. The full extent of the spec is a current focus of enquiry for us, but realistically, it is simply impossible to cram the equivalent of today's top-end PC graphics hardware into a console-sized, mass-market box.

Everything we've heard positions PlayStation 4K as a machine capable of playing current and next-generation ultra HD media, while also offering support for other aspects of the 4K spec, such as high-dynamic range and a wider colour gamut - aspects of the 4K spec that could be introduced to gaming. However, in terms of additional computational power, we've got be realistic about what Sony can deliver with a mid-generation refresh.

We can say that with some degree of certainty because PlayStation 4K will almost certainly use an evolved version of the APU technology used in the current console. Once again we will see semi-custom versions of AMD's CPU and GPU technology integrated into a single, console-friendly processor, and thanks to the firm's openness with its technology roadmaps, we have a good idea of the base building blocks Sony has access to in building its next PlayStation.

We also know about the fabrication technologies available. PlayStation 4 and Xbox One arrived when 28nm microprocessors were firmly established, and right now the industry is moving on to 14nm and 16nm chips using 3D 'FinFET' transistors. Shrinking transistors and innovative new architecture are what make generational leaps in computational power possible.

Knowledge of both of these areas, along with the idea that the device has to fit into a console form-factor, not to mention the compatibility required with the existing PlayStation 4, narrows the amount of options Sony has available significantly. But the real question is why both Sony and Microsoft are seemingly open to the idea of producing mid-generation refreshes of their consoles.

Perhaps the answer can be found in the slide above produced by AMD, showing the major generational improvements in silicon chip production technologies over the last decade. The bottom line is clear - the ability to shrink microprocessors and cram more transistors onto them, making them more powerful, is slowing down. By necessity, consoles may need to move onto a refresh cycle - a process of gradual improvement as opposed to generational leaps in performance. Just like PC hardware, in other words.

In Theory: PlayStation 4K - What Should We Expect?

From our perspective, we see three viable routes forward for a potential PlayStation mid-generation refresh.

Option #1: A new, more powerful PlayStation

The current-gen console processors are an assemblage of off-the-shelf AMD components with some level of customisation requested by Sony. In the move to 14/16nm production technology, there's a 2x increase to transistor density compared to 28nm, meaning that Sony can produce a microprocessor the same size as PS4's current Liverpool chip, but theoretically twice as powerful. Sony could also stand to benefit from AMD's advances in both CPU and GPU technology - its upcoming Zen CPU cores and Polaris GPU architecture.

However, the question of which parts are available to Sony comes down to timelines. Polaris is viable but difficulties may arise in terms of the new APU's CPU component. AMD's Zen architecture releases first as a performance desktop part towards the latter end of this year - consoles rely on low-power mobile technology, and the PC equivalents remain unclear, with no mention on AMD's roadmaps. There's a very strong possibility that a 2017 revised PlayStation could feature a relatively big jump in GPU performance, but conversely, the CPU component could remain much the same.

We know a little - but still not much - about Polaris, AMD's new GPU component, due later this year. We know that it's based on a fourth generation iteration of its GCN architecture, we know that AMD is promising a radical improvement in performance per watt (a mixture of design improvements, plus the move to 14nm FinFET fabrication technology), and we know that two processors have been designed - Polaris 10 and 11 - aimed at mainstream and higher-end markets. Think of them as today's equivalents to GCN's initial launch in 2011/2012 with the arrival of the Radeon HD 7970/7950 (codename Tahiti) and Radeon HD 7870/7850 (Pitcairn).

But here's the rub - everything we're hearing suggests that Sony is expecting this console to be paired with a UHD display. However, realistically, achieving even a 2x increase in GPU power compared to the current PS4 would be a remarkable achievement. To fit into a console-sized box, even this may be too optimistic.

Making life more difficult is the need for a bump to the surrounding memory architecture. More memory would be required to get more out of 4K resolution (higher quality textures), but more than that - faster RAM is required to service a more potent GPU. We aren't hopeful of a massive bump here, owing to cost issues. Other faster technologies - like HBM for example - exist but remain too expensive and aren't ready right now for show-time in a console.

From the media side of things, we would expect Sony to support HDMI 2.0, offering 4K video output at 60Hz along with the HDCP 2.2 content protection scheme - so Netflix at 4K on this unit would be no problem. We would not be surprised to see a next-gen 4K Blu-ray player in there either.

What we might expect:

• An APU with a higher-end Polaris would push graphics on - a 2x performance boost in GPU power compared to PS4 is achievable in a console form-factor. Possibly more - we really need to see the desktop PC equivalent parts first.
• By default, Polaris has support for 4K, HDMI 2.0, HDCP 2.2 and HDR.
• Console would not be cheap owing to the size of the processor - conceivably on par with PS4's £359/$399 launch price.
• Possibly higher depending on how much Sony pushes the boat out in terms of processor size and memory allocation.
• This PS4K could co-exist with a cheaper 'PS4 Slim' based on the older APU, again using 14nm/16nm technology.

The bottom line: In 2017, production technologies on 14/16nm should be more mature, and a significantly more powerful PlayStation could be released. But the pace of technological progress in the PC space isn't as rapid as it is on mobile. It took four dramatic leaps in chip production technology to make the generation leap between PS3 and PS4 possible. By 2017, there will have only been one viable jump in fabrication technology available to console manufacturers, and expectations should be limited. Actual 4K games will be in very short supply.

Option #2: PlayStation 4 evolved

Sony is sitting pretty with this console generation. PlayStation 4 is effectively the lead platform for developers on multi-platform titles. A potential danger in making PS4K too different from the older model is that developmental resources would be split, and software quality for the existing PS4 could slip. PS4K has to walk a tightrope - it has to offer something new to the core enthusiasts that propelled the original model to success, but at the same time, a 40m-strong userbase can't be left behind.

On a more practical level, there's also the question of compatibility. Sony offers low-level access to the PS4 graphics hardware via its GNM API - the danger in moving across to a new Radeon architecture is that incompatibilities may be introduced. Therefore, an option open to Sony with 14/16nm microprocessor technology is the ability to scale up the existing chip and bolt on some 4K-friendly features.

Short of an increase in clock-speeds, there's not a great deal that can be done with PlayStation 4's existing Jaguar CPU cores. However, there is much more fertile ground in the GPU component. The existing PlayStation 4's GPU is a semi-custom version of the Radeon HD 7870 - down-clocked and with two deactivated compute units. Other, larger GCN parts of the same generation are available - the 7970's Tahiti processor is the obvious example, offering up a 60 per cent increase in compute power. This could be combined with an overclock, faster RAM - and possibly more of it (though we suspect that cost issues may be a concern here). AMD's Tonga processor - Tahiti's replacement - may also be compatible enough, offering up some useful new features the PlayStation could really use, like delta compression to get more out of the memory bandwidth.

By PC graphics standards, this would be a highly conservative design - but it can be matched with 4K media functionality, HDR and wider colour gamut support - all the goodies we expect to see as standard in 4K screens due in 2017. And it must be remembered that both PS4 and Xbox One were considered conservative by PC enthusiasts at launch. Whenever a new console is mooted, there's always the temptation to look at the best of the best in terms of available PC parts - but these simply cannot be integrated into a console form-factor, or else they are simply not cost-effective.

What we might expect:

• We'd see a new PlayStation playing host to the same titles as the current one, but with visual improvements.
• Conceivably, older games may run more smoothly by default, or could be patched to access the newer hardware.
• Resolution could be pushed beyond 1080p and could look good on a 4K screen, but native UHD visuals for triple-A titles are off the table.
• Wouldn't be as expensive as the first option.
• State-of-the-art 4K media support, but harder to sell to all but the most hardcore gamers.

The bottom line: Scaling up and enhancing the current PlayStation doesn't sound particularly exciting and we do have to wonder what the point would be of a PS4K with very little chance of servicing 4K gaming. However, this is the design that stands the best chance of offering a decent bump to system capabilities without introducing too much in the way of compatibility issues. Our gut feeling right now (nothing more) is that this is the form the current prototypes take.

Option #3: PlayStation plus

A potential PlayStation 4K could very well be a PS4 Slim, with the existing APU shrunk to a 14/16nm production process, enhanced with minor boosts to functionality.

Since the processor needs to be redesigned anyway for the node shrink, Sony could take this opportunity to modernise some of the fixtures and fittings in the APU to provide better support for 4K displays - so a wider gamut, HDR, HDMI 2.0 and HDCP 2.2 could be added to the existing APU relatively easily.

Assuming Sony is simply refining its existing processor, as opposed to creating a newer, larger one, an alternative option would be to rule out a Slim chassis, keeping the current form-factor instead. The option exists to simply overclock the existing chip once it has been shrunk to 14/16nm. Less likely - but still doable, depending on chip yield - is the idea of unlocking the two blocked-off compute units on the current design of the APU, adding an additional 11 per cent of computational power to the GPU. To maximise any increase in graphics power, Sony would likely switch up its GDDR5 memory to faster modules - just as AMD does with its higher-end desktop graphics cards.

What we might expect:

• Full compatibility with 4K screens, including next-gen media.
• Complete 'no worries' compatibility with existing PlayStation 4 library.
• HDR support for gaming on 4K displays - even if gaming resolution remains at 1080p.
• Opportunity to lower cost as 14/16nm chips become cheaper.
• Unlikely to alienate the existing userbase - any performance upgrade would be more 'nice to have' as opposed to essential.

The bottom line: PS4K could simply be a smaller, leaner version of the existing hardware, with revised 4K media and (potentially) HDR support. The option exists to overclock the existing architecture and perhaps unlock the full potential of PS4's APU. It would be like an 'Elite' version of the existing console - nice to have, but not a generational or even half-generational upgrade in terms of processing power. The question is, assuming a 2017 launch, would that be enough?

What's the point of a mid-generation refresh?

In truth, when we first read the reports of a new PlayStation, we couldn't quite believe that Sony would already be calling time on what is shaping up to be its most successful console yet, especially when it seems that the current generation still has so much to offer. But regardless, this seems to be the way forward and Microsoft has already put its cards on the table.

"We see on other platforms whether it be mobile or PC that you get a continuous innovation that you rarely see on console," Phil Spencer said recently. "Consoles lock the hardware and the software platforms together at the beginning of the generation. Then you ride the generation out for seven or so years, while other ecosystems are getting better, faster, stronger. And then you wait for the next big step function.

"When you look at the console space, I believe we will see more hardware innovation in the console space than we've ever seen. You'll actually see us come out with new hardware capability during a generation allowing the same games to run backward and forward compatible because we have a Universal Windows Application running on top of the Universal Windows Platform that allows us to focus more and more on hardware innovation without invalidating the games that run on that platform."

It's not a particularly compelling argument up against all the advantages we've come to expect from the concept of coding to a fixed platform console - and we can't help but feel sceptical. Based on the technologies available, the tangible benefits seem unclear - it's unlikely that 30fps PS4 games will transform into 60fps PS4K games, and while we may see enhanced visuals and a push to extract the best from next-gen 4K displays, actual UHD native resolution gaming is simply not possible on cutting-edge titles, based on the technologies available to Sony now or in the next couple of years. True innovation on the newer hardware will also be held back by the need to the service the existing console, where the majority of the userbase will be.

Fundamentally, what new gameplay experiences can a revised console offer? At what point do you stop supporting the older PlayStation 4? We can perhaps see the case for an 'elite' version of a games machine - a love-letter to the hardest of the hardcore, with enhanced performance and visuals on the same games. But it reeks of niche appeal - and some might say that the PC already does a better job of servicing this need. When and if refreshed console hardware is officially revealed, it's going to need one hell of a killer app.