Freeing Up Resources: The PS4's Dedicated Units
Another thing the PlayStation 4 team did to increase the flexibility of the console is to put many of its basic functions on dedicated units on the board -- that way, you don't have to allocate resources to handling these things.
"The reason we use dedicated units is it means the overhead as far as games are concerned is very low," said Cerny. "It also establishes a baseline that we can use in our user experience."
"For example, by having the hardware dedicated unit for audio, that means we can support audio chat without the games needing to dedicate any significant resources to them. The same thing for compression and decompression of video." The audio unit also handles decompression of "a very large number" of MP3 streams for in-game audio, Cerny added.
At the New York City unveiling of the system, Cerny talked about PlayGo, the system by which the console will download digital titles even as they're being played.
"The concept is you download just a portion of the overall data and start your play session, and you continue your play session as the rest downloads in the background," he explained to Gamasutra.
However, PlayGo "is two separate linked systems," Cerny said. The other is to do with the Blu-ray drive -- to help with the fact that it is, essentially, a bit slow for next-gen games.
"So, what we do as the game accesses the Blu-ray disc, is we take any data that was accessed and we put it on the hard drive. And if then if there is idle time, we go ahead and copy the remaining data to the hard drive. And what that means is after an hour or two, the game is on the hard drive, and you have access, you have dramatically quicker loading... And you have the ability to do some truly high-speed streaming."
To further help the Blu-ray along, the system also has a unit to support zlib decompression -- so developers can confidently compress all of their game data and know the system will decode it on the fly. "As a minimum, our vision is that our games are zlib compressed on media," said Cerny.
There's also another custom chip to put the system in a low-power mode for background downloads. "To make it a more green hardware, which is very important for us, we have the ability to turn off the main power in the system and just have power to that secondary custom chip, system memory, and I/O -- hard drive, Ethernet. So that allows background downloads to happen in a very low power scenario. We also have the ability to shut off everything except power to the RAMs, which is how we leave your game session suspended."
