The PlayStation 4 is due out this fall, and its technical specifications have been largely under wraps -- till now. While the company gave a presentation at GDC, the system's lead architect, Mark Cerny, hasn't talked publicly in any great depth about the platform since its unveiling this February.

Cerny approached Gamasutra in the hope of delivering a "no holds barred PlayStation 4 hardware expose," he said, during the interview that resulted in this story. "That certainly is what we're here to do," said Cerny, before speaking to Gamasutra for well over an hour.

What follows is a total breakdown of the hardware from a developer's perspective: the chips on the board, and what they're capable of.

Questions on the UI and OS were off the table. What was up for discussion is what the system is capable of, and the thinking that lead Cerny and his team to make the decisions they made about the components they chose and how they function together.

To get to the heart of this deeply technical discussion, Gamasutra was assisted by someone with an intimate knowledge of how console hardware really works: Mark DeLoura, THQ's former VP of tech and now senior adviser for digital media at the White House Office of Science and Technology Policy.

The Beginnings

"For me, this all started in late 2007," said Cerny, remembering how he embarked on the road to becoming lead architect of the PlayStation 4. "Because we'd been doing postmortems on the PlayStation 3 -- a very broad group of people across the Sony Computer Entertainment team were evaluating how well that had gone."

That lead, naturally, to thoughts about what to do next. Musing on the architecture of Sony's next system, Cerny spent his Thanksgiving holiday reading up on the history of the X86 architecture -- realizing that not only had it evolved dramatically over the years, but that by the time the PlayStation 4 shipped, it would be powerful enough for Sony's needs.

It had evolved into something "that looked broadly usable by even the sort of extreme programmers we find in the games business," he said.

Realizing how passionate he was about the PlayStation 4 project, after Thanksgiving, Cerny went to Sony's then-execs Phil Harrison and Masa Chatani, "and asked if I could lead the next generation effort. And to my great surprise, they said yes."

"The Biggest Thing" About the PlayStation 4

Cerny approached the design of the PlayStation 4 with one important mandate above all else: "The biggest thing is we didn't want the hardware to be a puzzle that programmers would be needing to solve in order to make quality titles."

The PlayStation 3 was very powerful, but its unfamiliar CELL processor stymied developers. "There was huge performance there, but in order to unlock that performance, you really needed to study it and learn unique ways of using the hardware," said Cerny.

That situation led directly to the PS4's design philosophy: "The hope with PlayStation 4 was to have a powerful architecture, but also an architecture that would be a very familiar architecture in many ways."

In fact, this is something Cerny returned to again and again during the conversation. "We want to make sure that the hardware is easy to use. And so having the familiar CPU and the familiar GPU definitely makes it easier to use," he said.

Later, when asked about whether Sony considers the fact that many third party developers will also have to create versions of their games for the next Xbox, his response was, "when I say that our goal is not to create puzzles that the developers have to solve, that is how we do well in a multi-platform world."

But ease-of-use is far from Cerny's only goal. As a 31-year veteran of the industry, he well knows that the PC will march onward even as the PlayStation 4 stays frozen in time.

"Ultimately, we are trying to strike a balance between features which you can use day one, and features which will allow the system to evolve over the years, as gaming itself evolves," said Cerny. The "supercharged PC architecture," that the team has come up with -- to use Cerny's term -- is designed to offer significant gains the PC can't, while still offering a familiar technological environment for engineers.

To design the PlayStation 4, Cerny didn't just rely on research, or postmortems of the PlayStation 3. He also toured development teams and spoke to middleware partners to find out precisely what they wanted to see in a next generation console. The result? You'll read about it below.

What Does 'Supercharged' Mean, Anyway?

The PlayStation 4's architecture looks very familiar, at first blush -- and it is. But Cerny maintains that his team's work on it extends it far beyond its basic capabilities.

For example, this is his take on its GPU: "It's ATI Radeon. Getting into specific numbers probably doesn't help clarify the situation much, except we took their most current technology, and performed a large number of modifications to it."

To understand the PS4, you have to take what you know about Cerny's vision for it (easy to use, but powerful in the long term) and marry that to what the company has chosen for its architecture (familiar, but cleverly modified.) That's what he means by "supercharged."

"The 'supercharged' part, a lot of that comes from the use of the single unified pool of high-speed memory," said Cerny. The PS4 packs 8GB of GDDR5 RAM that's easily and fully addressable by both the CPU and GPU.

If you look at a PC, said Cerny, "if it had 8 gigabytes of memory on it, the CPU or GPU could only share about 1 percent of that memory on any given frame. That's simply a limit imposed by the speed of the PCIe. So, yes, there is substantial benefit to having a unified architecture on PS4, and it’s a very straightforward benefit that you get even on your first day of coding with the system. The growth in the system in later years will come more from having the enhanced PC GPU. And I guess that conversation gets into everything we did to enhance it."

The CPU and GPU are on a "very large single custom chip" created by AMD for Sony. "The eight Jaguar cores, the GPU and a large number of other units are all on the same die," said Cerny. The memory is not on the chip, however. Via a 256-bit bus, it communicates with the shared pool of ram at 176 GB per second.

"One thing we could have done is drop it down to 128-bit bus, which would drop the bandwidth to 88 gigabytes per second, and then have eDRAM on chip to bring the performance back up again," said Cerny. While that solution initially looked appealing to the team due to its ease of manufacturability, it was abandoned thanks to the complexity it would add for developers. "We did not want to create some kind of puzzle that the development community would have to solve in order to create their games. And so we stayed true to the philosophy of unified memory."

In fact, said Cerny, when he toured development studios asking what they wanted from the PlayStation 4, the "largest piece of feedback that we got is they wanted unified memory."

"I think you can appreciate how large our commitment to having a developer friendly architecture is in light of the fact that we could have made hardware with as much as a terabyte [Editor's note: 1000 gigabytes] of bandwidth to a small internal RAM, and still did not adopt that strategy," said Cerny. "I think that really shows our thinking the most clearly of anything."