Above: PlayStation 4 console
The PS4 uses a 256-bit bus and a type of memory, GDDR5, that the fastest graphics cards utilize. The combination of the bus (which is wider than a 128-bit bus) and the faster memory results in a pipeline that resembles a rushing stream. It can send data through the chip at a rate of 176 gigabytes per second.
That’s fast, but it wasn’t the only option. Sony also had a choice of using a 128-bit bus with a more complicated memory structure. That memory could send data even faster and then store some of it inside a smaller eDRAM memory that was on the chip. The result could be a system with 1,088 gigabytes per second of bandwidth, or more than a terabyte of bandwidth. That seemed obviously faster than the 176-gigabytes-per-second option. But Cerny said the on-chip memory would be very complicated to manage. So his team went with the simpler approach. Microsoft, by contrast, chose this latter path for the Xbox One. And on day one of the PS4 launch, Sony’s developers should already know how to exploit the architecture.
By switching to the PC technology, Sony could gain huge benefits because developers would have tools immediately available for making titles. They could start working on the new game designs almost immediately and get to playable prototypes much faster than they could for the PS3. The result would be better, cheaper, and more timely launch releases.
But Cerny said that the graphics chip also took in advances that had emerged on the PC side. Using the ability to program the chip for non-graphics tasks, Sony saw a way to give developers a way to make their experiences more sophisticated over time. The non-graphics tasks that devs can program on the graphics chip will lead to richer titles over time, Cerny said. Those capabilities include decompression, physics, raycasting for audio, collision detection, and world simulation. The graphics chip could handle tasks that otherwise couldn’t be done in the machine, and that’s the path for improvement over time.
The choices that Sony made were far different from Microsoft’s. For the Xbox One, Microsoft invested heavily in the Kinect motion-sensor technology, which accounts for a large part of the cost. Sony did not include such a sensor in its base unit. That allowed the company to price its system at $399 while Microsoft will sell the One for $499. The Xbox maker is using the same x86 vendor, AMD, as Sony. But the Xbox One has a less-powerful CPU/GPU combination, analysts say.
Microsoft has an even more radically different technology — what it calls “cloud processing.” That means that the Xbox One will reach outside of the console to get more processing power from Internet-connected data centers — the cloud — to handle game-processing tasks. Sony isn’t using that approach, and it might have a tough time arguing that its console is better. After all, one of the highest-rated games of the 2013 Electronic Entertainment Expo was Titanfall, a Microsoft exclusive coming from Respawn Entertainment and Electronic Arts for the Xbox One.
Who made the right choices? We’ll find out when the games come out.
Here’s our other stories on Cerny’s speech:
Sony’s collaborative approach to PS 4 design
Mistakes of the PS 3
How Sony entrusted the PS 4’s design to an American consultant
Here’s a video of Cerny’s speech.