Inside the PlayStation 4 Pro with Mark Cerny

Roughly three years after launching the PlayStation 4, Sony is weeks away from releasing a bigger, better version: the PlayStation 4 Pro.

Despite a summer (and then some) full of leaks and speculation, Sony waited until last month to publicly unveil the Pro in New York. Even then, technical details about the console were sparse; this week, system architect Mark Cerny told Gamasutra and other members of the press that since New York he’s been waiting for the other shoe to drop.

“For New York, our feeling was that it would be nice to show sort of the consumer-facing experience: what the visuals look like,” said Cerny. “I knew when we were doing that, I knew that some day, we'd have to go through the other half -- and that's today.”

What follows is an attempt to distill the salient points Gamasutra gleaned from a significant amount of time spent with Cerny going over the technical specifications of the PlayStation 4 Pro. Very little of this was public knowledge before today, and it should help developers better understand what the PS4 Pro can do, why it was designed the way it was, and what sort of time and effort is required to get your game to a place where it can take advantage of the console’s extra power.

Even if you aren’t planning on making a game for the PS4 or PS4 Pro in the foreseeable future, the way Cerny talks up the hardware is worth studying because it sheds light on how Sony is trying to sell the revamped console to the public -- and thus, in a sense, where Sony sees itself in the contemporary game market.

"PS4 Pro is not the start of a new generation"

Perhaps most tellingly, Cerny is very careful to describe the Pro as anything other than the harbinger of a new generation of consoles.

“PS4 Pro is not the start of a new generation,” he said. “And that is a very good thing.”

It’s a good thing because, he argues, a new generation of consoles is defined by chaos and novelty -- new hardware with new CPU architectures, new controllers, new GPUs, and all-new ways of designing (or selling) games. Such shake-ups often have significant benefits for the game industry at large, as well as significant costs. 

Cerny recalled how the PlayStation 1’s launch drove many devs to transition from 2D to 3D and from cartridge to CD-ROM games, noting that a significant number of developers foundered or exit the industry entirely because they couldn’t find success in a 32-bit world.

“It was certainly rewarding for players, but it was a true learning experience for the development community,” said Cerny. “At the time I estimated that, just by looking around, something like a quarter of the people involved in making games had to transition out of the business because they couldn't get familiar enough with the new tools and technologies.”

He went on to point out the different, novel demands that every generation of console hardware has placed on devs, before coming around to the PlayStation 4 -- which, as he told Gamasutra three years ago ahead of its launch, was explicitly designed to make devs’ lives easier by doing away with the PlayStation 3’s idiosyncratic Cell technology in favor of a much more approachable x86 architecture.

The PlayStation 4 Pro uses the same architecture as its older sibling, and thus, by Cerny’s definition, it’s not the start of a new generation -- just an attempt to breathe new life into the current one. It’s also, he was careful to state repeatedly, not the death knell for console generations as we know it.

“We don't believe that generations are going away. They are truly healthy for the industry, and for the gaming community,” he said. “It's just that the objectives for PS4 Pro are quite different.”

Put simply, those objectives are better performance and graphical quality, for both games and other media.

“PS4 Pro's targets are support of high-res displays, 4K displays, higher framerates,” said Cerny, “And 4K streaming, for those people who use PS4 for video, which is actually very big for us. It's the number two use for the console - streaming video.”

We’ll get into how the console is built to hit those targets in a moment, but before we do it’s worth considering what a (relatively) novel move this is for Sony. If you could travel back in time (oh, if!)  to 3 years into any PlayStation console’s lifespan, you could probably find some number of devs and players wishing it was more powerful. 

The fact that Sony is only now attempting a mid-cycle refresh suggests both that such a revamp is easier to do on the PC-like hardware powering the PlayStation 4 -- and that Sony itself is under increasing pressure to deliver better performance at a time when it has never been easier to build/buy a PC that handily outperforms the PS4.

With all that in mind, know that the PS4 Pro is effectively an upgraded PS4 with more GPU power, a souped-up CPU and a bit more memory, as well as some other more technical tweaks.

Cerny says devs shouldn’t expect to have to invest a lot of extra effort into modifying their games to take advantage of the Pro’s enhanced capabilities; minimizing that investment was, in fact, a core goal of the console’s design.

“As a mid-generation release, we knew that whatever we did needed to require minimal effort by the developers,” he said. “ In general, our target was to keep the work needed for PS4 Pro support to a fraction of a percent of the overall effort of creating a game. I believe we have achieved that target.”

“Also, as a mid-generation hardware release, we wanted to have something that would have complete interoperability with the standard model,” he continued. “To put that a different way, we knew we couldn't go back to the teams that created the 700 or so existing games [on PS4], and ask some significant percentage of them to open up their codebase and make it work properly on the [PS4 Pro.] The games just needed to work. At the same time, the console needed to have a high impact for the consumers, so we chose to focus on improved graphics, including better support for new TV formats and smoother framerates.”

One GPU becomes two

So while the PS4 Pro has a GPU capable of delivering “4.2 teraflops” of power, making it 2.28 times as powerful as the PS4, Cerny says there’s no new architecture in play. Instead, Sony doubled down on the PS4’s AMD GPU -- literally.

“We doubled the GPU size by essentially placing it next to a mirrored image of itself, rather like the wings of a butterfly,” he said. “That gives us an extremely clean way to support the 700 existing titles, because we can turn off half the GPU and just run something that's very close to the original GPU.”

But literally doubling the onboard GPU would seem to afford devs just double the power -- so how does Sony claim the PS4 Pro can do 2.28 times as much as the PS4?

“We were also able to take advantage of silicon process improvements and boost the frequency by 14 percent, to 911 MHz, which is what gets us from 2x the power to 2.28x the power,” said Cerny. “Additionally, we've added in a number of AMD roadmap features and a few custom features. Some of these give us better efficiency when rendering for high-resolution displays. We also have support for more efficient rendering for PlayStation VR.”

Among those “roadmap” features (features slated to come to AMD’s own discrete GPU chipsets in the future) are things like delta color compression, or DCC.

“DCC allows for inflight compression of the data heading towards frame buffers and render targets, which results in the reduction of the bandwidth used to access them,” said Cerny. “Since our GPU power has increased more than our bandwidth, this has the potential to be extremely helpful.”

There’s also a primitive discard accelerator which  “improves the efficiency with which triangles that are too small to affect the rendering are removed from the pipeline” and a work distributor, something Cerny says is critical once your GPU gets to a certain size because it functions as “a centralized brain in the GPU that intelligently distributes and load-balances the geometry being rendered.”

“The work distributor in PS4 Pro is very advanced,” he claimed. “Not only does it have the fairly dramatic tesselation improvements from Polaris [AMD’s GPU architecture], it also has some post-Polaris functionality that accelerates rendering of scenes with very small objects. “

But Cerny seemed more excited about another one of these “post-Polaris” features that the PS4 Pro has: a significant improvement in the way it handles 16-bit variables like half-floats.

With the PS4 Pro, said Cerny, “it's possible to perform two 16-bit operations at the same time, instead of one 32-bit operation. In other words, with full floats, PS4 Pro has 4.2 teraflops of computational power. With half floats, it now has double that -- which is to say, 8.4 teraflops of computational power. As I'm sure you understand, this has the potential to radically increase the performance of games.”

(Surely, you understand.)

Speeding up the CPU

As far as the PS4 Pro’s CPU goes, well, you already know it’s the same 64-bit x86 8-core “Jaguar” AMD CPU that drives the PS4, and now you know that Cerny and Sony feel that makes the PS4 Pro an extension of the PS4 generation rather than a new one unto itself. The PS4 Pro’s CPU has had its frequency raised “as high as it could go on the new process technology,” according to Cerny, which is about 2.1 Ghz.

That’s roughly 30 percent more CPU power than the 1.6 Ghz the PS4 is capable of, and Cerny says Sony has had to add a bit more cooling to the system to compensate for the fact that the PS4 Pro CPU is capable of running hotter than the PS4 CPU.

And like the PS4 Pro GPU, Cerny says the CPU is designed to easily accommodate games which aren't built to support it.

“What we do for the legacy games, if you want to play a game from 2-3 years ago that hasn't been patched or tested, is we just run that at 1.6 gigahertz,” said Cerny. “We run the GPU at 800 megahertz, and we shut down half of the GPU.”

Adding a bit more memory -- and changing how it's used

Last but not least, the PS4 Pro has a bit more onboard memory than the PS4 -- 1 GB, to be exact, though it’s 1 GB of “slow, conventional DRAM” instead of the 8 GB of GDDR5 RAM already in the PS4. Alongside that,  the PS4 Pro’s 8 GB of GDDR5 RAM has gotten a roughly 24 percent frequency boost, in Cerny’s estimation, so that it now runs at roughly 218 gigabytes per second.

“High-resolution graphics do need more memory. Estimates of what would be needed to double the display resolution of games were in the 300 to 400 megabyte range,” said Cerny, justfying the 1 GB addition. “But adding memory is a double-edged sword. With more memory it's possible to have higher-resolution textures and more detailed models, but that requires developers to create those assets. If we go that route, rather than asking the developers for an increase of a fraction of a percent in their effort, we end up with them needing to spend [much more] on assets.”

So in essence, devs get a bit more memory to play with -- but not too much more.

“We felt games needed a little more memory, about ten percent more. So we added about a gigabyte of slow, conventional DRAM to the console,” said Cerny. Sony also changed up the way the PS4 handles applications in memory:

“On the standard [PS4], if you're swapping between an application like Netflix and a game, Netflix is still resident in system memory, even when you're playing the game. We use that architecture because it allows for very quick swapping between applications. It's all already in memory,” said Cerny.

“On PS4 Pro, we do things a bit differently. When you stop using Netflix, we move it to the gigabyte of slow, conventional DRAM. Using that sort of strategy frees up almost a gigabyte of our 8 GB of GDDR5. We use 512 megabytes [of that] for games, which is to say that the games can use 5.5 GB rather than 5 GB. And we use most of the rest to make the PS4 Pro interface 4K, rather than the 1080p it's been to date. So when you hit the PS4 button, that's a 4K interface.”

PS4 Pro is built for a world where 4K TVs are popular and devices come out every 2-3 years

4K-resolution displays are, if it’s not clear already, one of the primary reasons why the PS4 Pro exists. That, and high dynamic range (HDR) rendering technology; Cerny said that unlike the PS4, which was inspired in large part by developers’ requests for a more approachable platform than the Cell-powered PS3, the PS4 Pro is a result of Sony reacting to how the consumer technology market has changed -- and where it thinks that market is going.

“PS4 Pro is, in this case, is more motivated by us looking at the rapid evolution of display devices,” he said. “We're very excited by 4K and HDR. And also looking at the innovation cadence in the rest of the world, in smartphones and tablets, where fun new things come out every two or three years.”

(“I do still talk to developers a lot,” Cerny also said. “I did a tour last year, I talked to a hundred and thirty people.”)

So yes, as many have speculated, the PS4 Pro is absolutely inspired by the success of bi-yearly (or even yearly) hardware release schemes in the mobile market -- most notably Apple’s iPhone/iPhone S release cycle. However, here again, Cerny is anxious to reassure developers that he doesn’t think console generations are a thing of the past; they’re just evolving a bit.

“I believe in generations. Generations are a good thing,” he said. “So, philosophically, we believe in them. We believe they continue, and this is a mid-generation release.”

Sony expects devs to support PS4 Pro, but there are no hard and fast rules -- just "conversations"

Thus, following the PS4 Pro’s release, Sony expects every PS4 game developer to release games capable of supporting both the base PS4 and the PS4 Pro (this is typically pitched as two separate modes, though Cerny notes it could well be three separate modes if your game has one mode for the PS4, one for PS4 Pro hooked up to a 4K TV and a third for a Pro hooked up to a non-4K TV.)

“For titles from PS4 Pro launch onwards, we're asking for direct support of 4K TVs and 1080p TVs,” said Cerny. “We're leaving it up to the developers, how they did that. Presumably 4K is high-resolution modes, and HDTVs is that scaled down, or maybe they have different modes with framerate options, or the like. I'm expecting that virtually all titles have those two different modes on PlayStation 4 Pro.”

“So we're going to let the developers determine it,” he continued. “We want something for people who have 4K TVs, and something for people who have 1080p TVs. Really, there are so many choices: For 4K TVs, yes we'd like them to have super high-resolution. But if [devs] also wanted to have lower-resolution graphics and higher frame rate, that would be very nice too. And so we encourage that. And for HDTVs, if they want to do framerate that's great, if they want to do graphics that's great.”

And if your game is already out (or will be out before the Pro), Sony is asking even more gently for PS4 Pro support -- basically, it would be great if you could find the time to make it happen, but it’s not required.

“With our evangelism, we don't have rules,” said Cerny. “We do ask people to take approaches for supporting the hardware. With regards to patches, we're very happy to get pretty much any support. If they'll open up their codebase and do something for PS4 Pro, we're very happy.”

He went on to point out Epic Games’ free-to-play MOBA Paragon as an example, since it’s been patched (as of this writing) to support PS4 Pro via a bunch of graphical enhancements -- but no native 4K support; instead, PS4 Pro owners playing Paragon on a 4K TV will see a scaled-up version of the game.

“I'm very happy with Paragon, even though there is no 4K support,” said Cerny. He went on to highlight a number of other PS4 games that have been patched to support Pro, and two rendering techniques in particular that he thought were very exciting ways to render games capable of dynamically scaling to play on two different hardware configurations: geometry rendering and checkerboard rendering.

“Like two-thirds of the games [on display at the PS4 Pro launch event last month] are using checkerboard rendering to hit the higher resolutions, and I think there is a bit of a debate raging as to what it is and what it means,” said Cerny. “Checkerboard rendering was used on PC by Rainbox Six Siege, by Ubisoft -- that's [what was explained in] the GDC talk that was given this year. What we've done is added specific hardware support, in the form of an ID buffer and a few more things, that allow it to go to that next level.”

And according to Cerny, the amount of effort required to implement PS4 Pro support for games like Days Gone, Horizon: Zero Dawn or InFamous: First Light was minimal -- at least by big-budget studio standards.

"Most of the work goes into implementing, in the case of these three titles, checkerboard rendering, in order to get the resolutions up to 2160p, or close to 2160p. And that hasn't been that much," said Cerny. "The initial implementation of checkerboard rendering for each of these titles was 3 weeks, for each of them, by 1 programmer. And you know, these are games where, these days, a typical game will have 100 people, 300 people, for years on end. So we're talking about 1 programmer for a couple of weeks. It's not too much."

But what if you don't have a team of hundreds? What if you're an independent developer with a small team, or are working solo, and you can't afford to lose three weeks of time building support for the PS4 Pro into your game?

"Well, when I say it's 3 weeks of work, yes, in some games that can be significant," Cerny acknowledged. "We don't have rules, though; we have conversations with the developers. So definitely we'd encourage them to take a look at what they can do in this context. But it's not mandated." 

He went on to laud Thekla's efforts to patch The Witness so that it renders at a higher resolution when played on a PS4 Pro, even on non-4k displays. "I was really happy to see that. But that's kind of what you're talking about, is it's a smaller title, and will the team go ahead and take the effort? The thing is gorgeous on an HDTV, I'm sure it's going to be even more gorgeous in 4K."

When Cerny spoke with Gamasutra three years ago about his work on the original PlayStation 4, he recalled how he had originally expected to move away from game development for a bit to focus exclusively on architecting a new console -- but soon found himself being drawn back into game development,

"I ended up having a conversation with [former Sony exec] Akira Sato, who was the chairman of Sony Computer Entertainment for many years," Cerny recalled, back in 2013. "And his strong advice was, 'Don't give up the software, because your value is so much higher to the process, whatever it is -- whether it's hardware design, the development environment, or the tool chain -- as long as you're making a game."

So it seems pertinent now to ask -- is Cerny still an active force in game development? Is he working on anything that informed the PS4 Pro's design?

"I'm definitely still continuing to work on games," he told Gamasutra, noting that he's now (publicly) contributing to Kojima Productions' inaugural game and (not so publicly) contributing to a few other games besides. However, he's been relying more on the input of other Sony devs who work closer to the hardware for insight into how to design the Pro.

"With PS4 Pro, mostly it's been...I've gotten a good handle on what the additional work is that's required, because [another] guy that's on the team that I'm on is doing the work," he said. "I'm not on InFamous or Horizon, for example." 

And for developers still on the fence, Cerny's argument for embracing the PS4 Pro seems simple: he's worked hard to minimize the extra effort required, and support for Pro likely makes your game more appealing to folks who buy the new (but not too new!) console.

"The target was to make sure that support [for the PS4 Pro] could be done for a fraction of a percent of the overall effort," Cerny said. "And I do mean a fraction of a percent. I mean, I've run the math, and it's 0.2 or 0.3 percent for these projects -- some of them. So at that point, I think it's very natural for the development community to support the platform."