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.
"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."
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.)